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Apple Discontinues ZFS Project

Zaurus writes "Apple has replaced its ZFS project page with a notice that 'The ZFS project has been discontinued. The mailing list and repository will also be removed shortly.' Apple originally touted ZFS as a feature that would be available in Snow Leopard Server. A few months before release, all mention of ZFS was removed from the Apple web site and literature, and ZFS was notably absent from Snow Leopard Server at launch. Despite repeated attempts to get clarification about their plans from ZFS, Apple has not made any official statement regarding the matter. A zfs-macos Google group has been set up for members of Apple's zfs-discuss mailing list to migrate to, as many people had started using the unfinished ZFS port already. The call is out for developers who can continue the forked project." Daring Fireball suggests that Apple's decision could have been motivated by NetApp's patent lawsuit over ZFS.

28 of 329 comments (clear)

  1. Great by tjones · · Score: 5, Funny

    Now if you're using zfs on Mac OS, you can't complain if it loses your data. You already knew it was forked.

  2. Re:God forbid... by mister_playboy · · Score: 5, Funny

    Please hand in your geek card as you leave.

    http://en.wikipedia.org/wiki/ZFS

    --
    Do what thou wilt shall be the whole of the Law ::: Love is the law, love under will
  3. The straight dope by Anonymous Coward · · Score: 5, Interesting

    Posting anon, lest someone guess who my sources are.

    The long and short of it was, Apple and Sun couldn't come to terms on the licensing. Sun wanted a lot of money for giving it to Apple under different terms and the amount they wanted was in the range of "hell, we could do it ourselves for that".

    Add to that, the Oracle buyout and Sun going into management paralysis, and Apple decided to go it alone.

    Apple's CoreOS team includes several of the lead engineers from the ZFS project (who fled the remnants of Sun in the Schwartz melt-down), and the architect of the BeFS. I'm expecting Apple to do their own next-generation file system, probably in the 10.7 timeframe.

    1. Re:The straight dope by Culture20 · · Score: 5, Insightful

      Why would they need different licensing terms?

      They probably wanted to rename it without changing it. Apple likes renaming things. Microsoft OTOH, loves using the same name as everyone else, and changing stuff to break interop.

    2. Re:The straight dope by segedunum · · Score: 4, Interesting

      The long and short of it was, Apple and Sun couldn't come to terms on the licensing. Sun wanted a lot of money...

      That doesn't make any sense. I fail to see why Apple should agree licensing terms for a CDDL licensed open source project or how Sun could demand money for the privilege. Sun were positively overflowing with love towards Apple (as they usually are) when they heard that anyone would actually be interested in their uber new filesystem.

    3. Re:The straight dope by dangitman · · Score: 4, Insightful

      Microsoft obviously wasnt on board for any of this, and without the momentum behind ZFS it never will.

      Microsoft is never on board for anything useful, so I'm not sure it really makes any difference.

      --
      ... and then they built the supercollider.
    4. Re:The straight dope by Robotbeat · · Score: 5, Interesting

      "The flip side is that I've heard that Apple's file systems team is full steam ahead on their own next-generation file system. And, perhaps not coincidentally, they're hiring." from http://daringfireball.net/linked/2009/10/23/zfs

      This is pretty shitty because it'll fragment the momentum ZFS had in being the next-gen ubiquitous file system. When it was clear ZFS wasn't coming to Linux, those guys got btrfs going, now Apple is doing their own, while ZFS obviously will stay around too. Microsoft obviously wasnt on board for any of this, and without the momentum behind ZFS it never will. This nonsense isnt helping, and I think the best Oracle could do it release it under all the licenses that'll get it into OSX/Linux and perhaps even Windows. Can Oracle go over Sun's head on this or Sun==Oracle?

      (emphasis mine)

      Unfortunately, btrfs isn't "going" anywhere. Guess who their development was funded by? That's right, Oracle! Notice that they haven't released anything new since BEFORE Sun's shareholders approved the acquisition? (Latest release on the btrfs wiki is v .19, released in June 2009) It's not exactly improving at a breakneck pace... If btrfs is going to go anywhere, they need some real development money.

      Dang Oracle.

    5. Re:The straight dope by ThePhilips · · Score: 4, Interesting

      It doesn't make sense to you. But it does to every other business.

      Free, open source software != costs nothing. (*)

      Sun wanted Apple to share development and maintenance costs. Apple wanted some long-term guarantees that Sun wouldn't stop development and would also help Apple to solve problems of ZFS under Mac OS X.

      Similar deals happen all the time.

      It's just this time the companies couldn't agree on price and/or terms. Obviously acquisition by Oracle contributed to the volatility of situation.

      (*) File system as file system is a rather trivial thing with well defined interface. ZFS is not only a file system, but also volume manager and network service. And long list of management tools for all that. Those are big money involved in development, maintenance and support of all that stuff.

      --
      All hope abandon ye who enter here.
    6. Re:The straight dope by setagllib · · Score: 4, Informative

      You really need to subscribe to the mailing list. The rate of development is only growing -- it's just now moved on to a lot of smaller features and improvements, now that most of the work is already done.

      --
      Sam ty sig.
  4. Re:God forbid... by Anonymous Coward · · Score: 5, Funny

    My sense of entitlement demands that everyone hand everything to me on a silver platter as well! I shouldn't be required to click on a link, much less do a Google search. You and I are in agreement. BTW, you owe me for that.

  5. The Reason is Probably Technical by segedunum · · Score: 4, Interesting

    I doubt that it's a legal issue as the primary reason that this has happened, especially considering that the project seems to have stagnated steadily in successive versions of OS X. There just doesn't seem to have been the will within the OS X development group to make this work and to support and fully integrate ZFS into the inner workings of the OS. Given the pretty extensive functionality and plumbing of ZFS its probably been too much of a big ask to integrate a filesystem like that into a desktop. They might well have come to the conclusion that ZFS was simply complete overkill on a desktop and that it just wasn't possible.

    However, they still desperately need a next generation filesystem and according to the linked article they're hiring filesystem engineers. I don't see any evidence that this was anything other than a technical avenue that they've explored that has fallen by the wayside as so many have before.

    1. Re:The Reason is Probably Technical by jcr · · Score: 5, Interesting

      There just doesn't seem to have been the will within the OS X development group to make this work and to support and fully integrate ZFS into the inner workings of the OS.

      I can't agree with that. Spend ten minutes with the filesystem engineers at WWDC, and you wouldn't come away thinking there was any shortage of will to make ZFS fly on the Mac.

      -jcr

      --
      The only title of honor that a tyrant can grant is "Enemy of the State."
    2. Re:The Reason is Probably Technical by segedunum · · Score: 4, Interesting

      ZFS is the next generation file system that all others will have to live up to.

      I'm sure it will, but I'm afraid that doesn't mean that made it practical for Apple to integrate into OS X or that it fitted the use cases they needed for many desktop scenarios. The FreeBSD people still haven't been able to run and integrate it reliably.

      I use it on servers daily at work, and I was looking forward to having it on my Macs at home. Bit rot is a very real problem. ZFS handles it automagically.

      The ZFS advocates trot those lines out every time and they're total nonsense. Ultimately, the only way to deal with silent data corruption or 'bit rot' is to have multiple levels of redundancy several times over for your data - which ZFS has and deals with. No desktop Mac can ever have that. Anyone who thinks that is anywhere near being practical to deal with on a desktop system is an idiot, and no, I'm afraid booting OpenSolaris with ZFS on your desktop system at home and not having it crash and burn does not even approach the kind of issues and corner cases that Apple's engineers will have to deal with, especially in a desktop system like OS X.

      By no stretch of the imagination does ZFS handle this 'magically'. There is a severe price to be paid. If you don't have redudancy then you will simply risk losing your ZFS pool if there is corruption.

      What handles failure at the data level? Nothing. Hope you make backups of your arrays.

      I'm afraid that hardware, bad sector and disk issues are far, far more prevalent problems than data corruption at an OS level. Many apparent corruption issues at the OS level are usually down to hardware issues somewhere down the line. It might be a problem for operating systems with fairly shitty and poorly maintained disk and controller device drivers with a poor history on x86 and widely used hardware (hello Solaris!) but I'm afraid it's just not a primary concern for everyone else or for those developing desktop operating systems.

    3. Re:The Reason is Probably Technical by 4iedBandit · · Score: 5, Informative

      I'm sure it will, but I'm afraid that doesn't mean that made it practical for Apple to integrate into OS X or that it fitted the use cases they needed for many desktop scenarios.

      Um, the technical work was already done. It could have shipped with Snow Leopard. Again, the reason it didn't has nothing to do with the technical feasibility of it.

      Ultimately, the only way to deal with silent data corruption or 'bit rot' is to have multiple levels of redundancy several times over for your data - which ZFS has and deals with. No desktop Mac can ever have that.

      Why? Because you say so?

      Anyone who thinks that is anywhere near being practical to deal with on a desktop system is an idiot

      While I may be an idiot, you have to convince me that ZFS is not practical for a desktop. Again, just because you say so is not reason enough. I stand by my statement that ZFS is the only file system with enough benefit to make me explicitly choose it for building servers. You may argue that there's a difference between a server and a desktop but those really are nothing more than abstract concepts. A file system that has too much overhead for my desktop has too much overhead for my servers. Performance matters. ZFS may not be the fastest, but it is no slouch either and the other benefits it brings to the table far outweigh miniscule performance concerns.

      By no stretch of the imagination does ZFS handle this 'magically'. There is a severe price to be paid.

      What exactly is this severe price? Can you spell it out? Exactly? "Any sufficiently advanced technology is indistinguishable from magic." In that respect yes I will say it is magic because it is head and shoulders more advanced than anything else I've had the pleasure of working with. File systems have not had this kind of improvement in decades.

      I'm afraid that hardware, bad sector and disk issues are far, far more prevalent problems than data corruption at an OS level...but I'm afraid it's just not a primary concern for everyone else or for those developing desktop operating systems.

      How do you know? It's not a significant problem till the data you need is unavailable when you need it. At home my own modest media library sits on just 500 Gig with no guarantee that any of it will still be whole in 6 months. Sure I back it up. Routinely. But until you access the file you don't know if it's been corrupted. Then how long as it been corrupted? Do your backups go back far enough to compensate? Yes you can checksum everything routinely and maintain a database of checksums to validate file change. Part of the beauty of ZFS is it does this with every thing you put in it, at the block level, and it validates the checksum every time you read the data. If a block fails the check, it not only sends you the valid block from the mirrored copy (You do have redundancy right? Even ZFS won't save you if you only have one copy.) but also replaces the bad block with a copy of the good one.

      Storage capacity is skyrocketing. Going to backup to fix problems is a real problem in itself. Are the tapes on-site? Do we have to go to the vault to find an uncorrupted copy? Did the media pool get recycled and now there is no uncorrupted copy? Do you enjoy explaining to an executive why the data they want is unavailable despite spending millions on enterprise class storage and backup solutions? The problems of enterprise storage are becoming problems of home users. I have three terabytes of storage just to backup my home system in a replication layout I'm okay with, but I really would have loved the protection ZFS offers against bit rot to top it off. Stick your head in the sand if you want, but I consider my data and it's availability a little more important. ZFS handles it elegantly, in the background, with negligible performance hit.

      --
      "The avalanch has already started, it is too late for the pebbles to vote." -Kosh
  6. Github project taking up the slack by KillNateD · · Score: 5, Informative

    Dustn Sallings put the code on Github and has already hacked some basic Snow Leopard support and a minimal installer:

    http://dustin.github.com/2009/10/23/mac-zfs.html

    Code's here, fork away:

    http://github.com/dustin/mac-zfs

  7. Re:God forbid... by NoYob · · Score: 5, Funny
    Holy shit!

    All this time, I thought folks were talking about file management with a phony French accent!

    Save zee file to zee FS and you will see that zee bytes go ...

    --
    It's NOT me! It's the meds! I'm on 1000mg of Fukitol.
  8. Another nextgen FS on the way? Hmmm. by Lemming+Mark · · Score: 4, Insightful

    Interesting - we're chugging happily along in Linux / Windows / Mac / Unix land having a load of competing filesystems where all the popular ones have *roughly* similar capabilities. Then ZFS appears in OpenSolaris and filesystem design becomes cool again. Everyone starts either porting ZFS or making filesystems with similar features ... Now a major player that actually *had* ported ZFS (somewhat) is seemingly deciding to go it alone. It seems as though the next-gen filesystem space is also going to have a variety of competing filesystems.

    I generally think this is a good thing, lets just hope that a reasonable degree of interoperability becomes possible anyway.

  9. Re:With SSDs, who needs it? by BoneFlower · · Score: 4, Insightful

    When SSDs come down A LOT in price, and up in size, maybe.

    Go do a search on Newegg. Biggest they've got is 256GB, of those, the cheapest is $595. You can get several terabytes for that price with a magnetic hard drives.

    SSDs have a place, but as a general replacement for magnetic hard drives they are too expensive with too little capacity.

    There is also more to the file system than access speed.

  10. This is devastating... by mysidia · · Score: 5, Funny

    Hearing that ZFS support was upcoming in Snowleopard is one of the things that encouraged me to switch my desktop from Windows XP to MacOS.

    It is an understatement to say i'm disappointed to see Apple abandoning this.

    Support for ZFS is not just a little feature checkbox, it's a major component of the OS.

    It'd be like if Microsoft dropped/cancelled support for Solitaire from Windows....

    1. Re:This is devastating... by mysidia · · Score: 5, Informative

      I tried the zfs commands you suggested but there aren't any of those available in my path,

      The two programs used to work with zfs are 'zfs' and 'zpool'. Both of them are normally located in /usr/sbin

      If your PATH is broken so you can't easily access the tools, it doesn't matter what filesystem you're using, you'll have a bad time. I would suggest adding /usr/sbin to your PATH if it's not, or else use "/usr/sbin/zfs list" etc.

      the user's, life is made harder?

      The user's life is not made harder. It's no harder to learn "Zfs list" than to learn "df"

      What is all so totally worth it? I haven't seen any advantages of zfs over hfsplus.

      Copy on write filesystem, performance is excellent..

      Unlimited impact snapshots which have no I/O performance impact, and has the ability to rollback to most recent snap, clone snapshot, etc; makes backup, replication type tasks easy. The ability to implement transactional unbreakable system upgrades, ala apt-clone.

      RaidZ, to protect against drive failure

      Ditto blocks and checksums to ensure data integrity, protect against silent data corruption, heal bad disk blocks.

      No need to 'fsck'

      No need to decide the size of each file system at creation time, 'quotas' are soft and can be changed, instead of having to re-format/fdisk to change sizes of a dataset.

      No need to manage individual disks. No limits on number of disks imposed by the filesystem layers.

      No arbitrary limits in zfs. ZFS can scale to (in theory) 256 quadrillion zettabytes. Other filesystems have a max file size limit, and a max filesystem size limit.

      Sharing a folder is a simple invokation of a "share" command.

  11. Re:Maybe they should look at HAMMER FS by Renderer+of+Evil · · Score: 5, Funny

    Steve Jobs commented on HAMMER FS inclusion in 10.7 during WWDC 2009. He said "due to legal and technical constraints we can't touch that"

  12. Correction by toby · · Score: 4, Informative

    A lot of confusion has resulted from labelling ZFS a "filesystem". It actually combines both volume management and filesystem layers to achieve unique levels of performance, manageability, and data protection. Merits close study, as the concepts of ZFS overtake current best practices, conventional filesystems and RAID. You can get this taste of the future today, if you're using Solaris 10/OpenSolaris/FreeBSD.

    --
    you had me at #!
    1. Re:Correction by SanityInAnarchy · · Score: 4, Insightful

      Modularity is a good thing, if you draw the modules in the correct place. And ZFS is indeed modular...

      Take all of this with a grain of salt, as I haven't actually used ZFS, only designed something similar, then found ZFS did it already, then decided I didn't care and used Linux anyway.

      My understanding is that there's a storage layer, where you can simply request storage for some purpose, and it gives you that storage with an id -- kind of like an inode. You could build a filesystem on top of that, managing all the metadata yourself. Or you could build something else -- a database, for example. And the filesystem layer still handles all kinds of things, like permissions, directories, etc, it's just that the allocation has been separated out.

      Thus, the allocation layer can make smart decisions about things like which disk to allocate something on, or what actually needs to be replicated, etc.

      For example: Think about any kind of RAID, even striping. If RAID can only work with whole volumes, that means the entire discs have to be synced (in RAID1) or checksummed/paritied (in RAID5), including free space. In ZFS, not only can you avoid replicating free space, but I believe you could also specify which files are important and which ones aren't -- and only the important ones are replicated, thus saving space on the ones which aren't.

      Another, more theoretical example: SSDs are a bunch of hacks on top of hacks. See, erasing and then writing to the same flash cell over and over wears it out, and there's no seek time. Largely because of Windows, I would guess, SSDs these days implement wear-leveling in the firmware, so that the OS sees only a logical disk that pretends to be a hard drive. But this means they always have to keep a number of cells unallocated, and it slows down writes to have to erase each cell before writing.

      So, someone came up with the ATA TRIM command, where the OS could tell the SSD which blocks are no longer in use, and the SSD can actually erase them.

      Compare this to the old solution -- implement wear-leveling in software. There were a few filesystems written to run directly on the flash, and it was actually the filesystem doing the wear-leveling. This meant the filesystem could intelligently spread new writes over free space, instead of having to keep some arbitrary number of blocks in reserve...

      This is getting fairly technical, and also boring, as ultimately, it's not that much of a difference. But this just shows the potential modularity of a system like ZFS. See, if ZFS separates out the allocation, that means you could replace that part without touching the filesystem, database, or anything else. And you could probably replace it with something that knows how to deal directly with a flash device -- something which, for example, erases blocks as ZFS snapshots are deleted.

      --
      Don't thank God, thank a doctor!
    2. Re:Correction by BitZtream · · Score: 5, Informative

      Warning: I have become a ZFS fanboy, my statements may not be entirely rational.

      Use ZFS for a week on something like a file server, you'll be more than willing to ignore traditional Unix logic (which I firmly believe in) in order to use the goodness that is ZFS.

      I'll admit, I'm a ZFS fanboy now, and I've only used it on FBSD 7.2, which is using a much older version of ZFS (v6, current is 13 I think). In 7.2 its not considered production ready and its still awesome to work with for me.

      I shoved 4 PATA and 4 SATA drivers in a case, 2 gigs of ram (really the minimum for FBSD and ZFS on a 64 bit machine, which is where it sings). The 4 SATA drivers are in the zraid vdev, 2 of the PATA drives are in another mirrored vdev, and the final 2 in a second mirror vdev. So all the drives have redundancy and they are all in one big zpool with the total space available as one big chunk.

      Now thats all well and good, but heres where it gets awesome. Want more space? Add some drives, create a new vdev, add it too the pool, instant space available. Okay, so thats not that impressive in and of itself. I can also add in a SSD as a 'cache' drive, which the ZFS system will then populate with a read only copy of data that gets accessed often in a random way, for a speed increase for your random IO needs.

      Okay, so I've got a few terabytes of data available, but I need a to create a share for backup using TimeMachine on my Mac. Well time machine will be happy to consume all the space on the drive. No problem, create a new mount point in the zpool, limit it to 1TB. It will only consume up to 1TB, IF space is available in the zpool. I can also reserve the space if I want to ensure its there for the backups. You can use the same system for quotas of individual users.

      I also have a bunch of ISOs with uncompressed data on them that I mount from virtual machines for various reasons, full of essentially text data. Welp, for that create another mountpoint on the same zpool, turn on compression, now my 5TB of text gets compressed into a few hundred gigs automatically and transparently. Its read only, and very important. I have backups, but they are in another state and transfering them back would be a painfully slow process which would cost me a lot of time. So I set the mount point to read only and set copies=2. Now the mount point is read only, and the data is stored twice, on 2 different vdevs. So not only is the data on a raid or a mirror, its on BOTH. If I was really worried I could set copies=3 and it would be on all the vdevs, so as long as one is usable I have my data, assuming all the vdevs have enough space to store the data. One of them doesn't, so copies=2 is the only useful option to me.

      I also have a software archive of all my commercial windows software, I want to keep it safe from any sort of infection or modification, so I set that mount point readonly.

      So far, I've done nothing that can't be done already with existing methods, but what I've done it across a common shared data pool. Free space is shared across all of them.

      I thought ZFS was a waste of time until I started using it. I am by no means a ZFS master, but I've learned that it can do some pretty powerful things. My setup is small, I only use it at home until FBSD 8 is released, which will have what is considered to be a production ready implementation, but I will be moving to it at that point in our internal office servers.

      I know I haven't listed any life changing reasons to use it, but its turned me into a fanboy.

      Technically, it IS modular, even if it doesn't have well defined zones. If you look at ZFS in a slight different way, it can be just one layer of the system. You can create virtual devices in a zpool and treat them as a block device (its just another /dev entry). Just to see how it worked, I created a virtual device on top of the zpool, formatted it with UFS, put some files on it, expanded the virtual device, ran growfs and had a larger UFS mount point.

      --
      Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
    3. Re:Correction by TheRaven64 · · Score: 4, Informative
      ZFS is modular, it just doesn't have layers in the same places at the conventional block device, filesystem, vfs layers.

      At the bottom layer, you have the pooled storage layer. This is comprised of several modules. The lowest layer is responsible for combining virtual devices into storage pools. This handles things like stripping and mirroring, but it does so with dynamically sized block ranges, rather than static ones (i.e. partitions). On top of this you have the transactional I/O layer. This handles things like checksums, encryption and compression, and provides support for transactions. Every disk access goes via this layer. That means that every single block device access from the upper layers gets transaction support, so you can guarantee that the block devices are always in a recoverable state; every group of low-level I/O operation either worked or failed, it never partially worked. Above this is the adaptive replacement cache, which handles caching and, with the L2ARC can also perform caching in Flash as well as RAM.

      On top of that, you have the transactional object layer. While the pooled storage layer works with a flat 128-bit address space, the transactional object layer works with objects and sets of objects. Any higher-level I/O is expressed in terms of transactions containing modifications to sets of objects. This is a very powerful abstraction. An object can be a complete filesystem, some metadata, or a file; there is no difference at this layer. Anything that you can do with one, you can do with any of the others. There are a few other things in this layer, like the ZFS intents log, which handles a higher-level (finer-grained) transactional model.

      On top of this is the user interface layer. There are two things here, the ZFS POSIX Layer (ZPL) and ZVOL. The former produces something that looks like a UNIX filesystem, with NFSv4 ACLs and a few other nice features. This is close to a filesystem in the traditional model, but also a bit like a VFS. It provides something that looks like UFS on top of lower-level features, but these are not on-disk structures. ZVOL is simpler; it provides something that looks like a block device. You can export this via iSCSI, for example, and put any kind of filesystem you want into it. Unlike a real block device, this one supports copy-on-write, snapshots, transactions, and so on. You can, for example, have a Windows VM (or real system) with a FAT or NTFS filesystem in a ZVOL mounted via iSCSI. You can snapshot it with the same O(1) snapshots that the rest of ZFS has, and then restore it later. You can also use zfs send and zfs receive to stream the changes across the network to another machine, irrespective of whether you're using ZPL or ZVOL + some filesystem. You can also use ZVOL for things like UDF images for burning, creating a skeleton image, cloning it, and using the native copy-on-write support to make small changes to it.

      --
      I am TheRaven on Soylent News
  13. Too bad [FOR APPLE], ZFS has some nice features by fnj · · Score: 4, Insightful

    Too bad for Apple, not for ZFS. OpenSolaris and FreeBSD support ZFS just fine. I do think it's best suited to servers, and OpenSolaris and FreeBSD are greatly superior server operating systems anyway.

  14. Re:Maybe they should look at HAMMER FS by nxtw · · Score: 4, Funny

    Thanks for breaking it down. Too bad Apple had to stop HAMMER time.

  15. Re:With SSDs, who needs it? by symbolset · · Score: 4, Interesting

    SATA attach SSD has achieved price parity with enterprise SAS, the density is almost there, and the performance completely blows it away. We're not at the end of spinning disc, but you can see it from here.

    The new performance tier of storage is PCIe attach SSD. At two terabytes of storage and 1.5GB/s per slot, we're getting close to what we used to get from Ramdisk in performance and adequate density at 3TB per rack unit including server (HP DL785 G5 or equivalent). Yes, this is expensive right now, but the performance tier always has been. This is for trading platforms, HPC and such. These are approaching 2M IOPS and 40TB per 7U server.

    The second tier is 2.5" 256GB SATA SSDs. You get 3TB per rack unit including the server. About the same cost as SAS for 10x the performance. Software options enable you to scale this to infinity in both bulk and performance. Great for databases, VMDK files and iSCSI. Get the hot-swap version and leave some open bays so that when the 1TB 2.5" SSDs come out you can migrate your LUNS with no downtime.

    The third tier is SAS spinning disk. At something like 20TB/Rack unit (excluding servers) you can use this to serve frequently used files.

    The fourth tier now is SATA spinning disk. At roughly the same density as SAS spinning disk for one-fourth the cost, this is a good candidate for deduplicated targets like virtual tape libraries or deduplicated NAS. It's also a good place to store your snapshots. With modern snapshot technologies there's no good reason to not store snaps every 15 minutes or so. Typically you would park this storage offsite for DR purposes so you can avoid the Premium Microsoft danger eXperience(**).

    Storage pros probably would note that I neglected to mention tape and Fiber Channel. That's neither accident nor ignorance. The only reason for tape is legally mandated tape backups, and I consider this the IT equivalent of legally mandated hitching posts outside every business (which laws persist in some places) - if you gotta, you gotta, but there's no reason any more to consider it a necessary or good practice. As for Fiber Channel, it just doesn't fit in the model any more. I know this hurts the feelings of folks who just dropped a million bucks for a single rack of SAN storage with 100TB, or worse - popped for the new 8GBit stuff complete with a converged ethernet/FCoE solution, but it's true. There's just no reason for fiber channel any more. It just doesn't have the bandwidth to support a modern storage solution and it costs too much. Sure, it's got redundancy from the disc to the file server, but so what: modern file servers use redundant storage and clustered redundancy and don't need the diminishing returns of embarassingly expensive drives, head nodes, capacity licensing and annual support contracts. By the time you figure in oversubscribed ports in your FC network, you've lost the supposed reliable performance benefit of the whole thing. This isn't bad news for Cisco - they're going to sell a lot of 10Gbit Ethernet ports before they get cheap and they haven't lost anything by being also compatible with FC. It really bites to be EMC this week, but they'll figure it out.

    Check the specs on this server, this card, this drive and this array. This is off-the-shelf stuff, not pie in the sky. The interconnect people need to get off their butts, but this is all doable right now. The compute side becomes an almost trivial cost of what it takes to maintain this storage bandwidth and capacity. If you like proprietary solutions HP sells a thing called the LeftHand Virtual San App

    --
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