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Is the Time Finally Right For Hybrid Hard Drives?
a_hanso writes "Hard drives that combine a traditional spinning platter for mass storage and solid state flash memory for frequently accessed data have always been an interesting concept. They may be slower than SSDs, but not by much, and they are a lot cheaper gigabyte-for-gigabyte. CNET's Harry McCracken speculates on how soon such drives may become mainstream: 'So why would the new Momentus be more of a mainstream hit than its predecessor? Seagate says that it's 70 percent faster than its earlier hybrid drive and three times quicker than a garden-variety, non-hybrid disk. Its benchmarks for cold boots and application launches show the new drive to be just a few seconds slower than a SSD. Or, in some cases, a few seconds faster. In the end, hybrid drives are compromises, neither as cheap as ordinary drives — you can get a conventional 750GB Momentus for about $150 — nor as fast and energy-efficient as SSDs.'"
If there is to be a time for hybrid drives, the window on it is fast closing. As SSDs get cheaper and cheaper more and more people will opt to just go that route. Most people don't really need massive HDDs and so if smaller SSDs get cheap enough that'll be the way they'll go. They don't have to be as cheap as HDDs, just cheap enough that for the size people need (probably 200-300GB for more people) they are affordable enough.
For me personally, the time already came and went. I was very enthusiastic about the concept of hybrid drives, particularly since I have vast storage needs (I do audio production). However no hybrid drive for desktops was forthcoming. Then there was a sale on SSDs, 256GB drives for $200. I picked up two of them. $1/GB was my magic price when I'd be willing to get them. Now I have 512GB of SSD storage for OS, apps, and primary data. That is then backed by 3TB of HDD storage for media, samples, and so on.
A hybrid drive has no place. I'd certainly not replace my SSDs, they are far faster than any hybrid drive (even being fairly slow on the SSD scale). Likewise I have no real reason to upgrade my HDDs, they serve the non-speed intensive stuff.
While I'm willing to spend more than most, it is still a sign of things to come. As those prices drop more and more people will say "screw it" and go all SSD.
I think the idea is cool. However, as you now get the best of both worlds (capacity, speed) you also have two areas of failure (mechanical damage, flash corruption). I also hope the firmware does not create problems. It's not completely unusable product either.
I don't imagine it is. Anandtech found it wasn't that difficult to evict stuff from the cache you actually wanted. Not to mention that if you start copying anything especially large (your MP3 collection, or installing a couple games from a Steam sale, say) you nuke the cache and are back to mechanical HD performance.
Personally, I prefer to do it manually. Stuff I want to load fast (Windows, applications, games, my profile folder) sit on an SSD. Bulk data sits on a mechanical drive.
Who is this for?
With only 4-8gb of flash I can't think of who this is for?
Mid-range consumer desktops/laptops?
Really with such little cache you might as well just add more ram.
Wouldn't even dream of putting one of these in a server. It's a shame linux doesn't have L2ARC support and it would be nice if there was a drop in hardware equivalent.
Not only are SSD prices going down, but traditional hard drives are going UP! (At least for the short term)
Prices taken from Newegg.com:
Seagate Barracuda XT 3TB is $399.99 (used to be a lot cheaper)
Seagate Barracuda 1TB SATA III:
About a year ago: On sale for $60, regular $70
Now: $149.99
I think now is the time of the SSD and the hybrid drive is just not worth the price
And considering this drive is retailed at $239.99 and a regular mechanical 750GB drive is between $69.99(Hitachi Deskstar) and $179.99(Western Digital Black) there is no reason to buy it.
Just go buy a small SSD and a regular mechanical drive and do it manually
If you're willing to make a bit of effort, that is.
Just yesterday I was just investigating the Highpoint Rocket 1220 and 1222 HBAs, which imbues its possessor with the power of Creation... the power to create hybrid magnetic-flash storage devices. Hook up an SSD and a good old moving-platter drive to it, and the HBA does the heavy lifting to create a virtual hybrid drive that will appear as a single device to the host system. It's similar to what is being done with some RAID enclosures of the last couple years, using chipsets like the JMicron JMB393 to create singular virtual drives that are really RAID arrays. I have no doubt there will be other brand HBAs of a similar sort joining these Highpoint ones soon enough.
With products like this Highpoint HBA, it's not necessary to be a lady-in-waiting to to some royal manufacturer's whim. You can pick and choose an SSD and disk drive of prices and capacities and characteristics that suit your specific needs, rather than waiting breathlessly for some one-size-fits-all solution that benefits the maker more than the buyer.
I would buy one now if they would implement it as a write-back cache. It wouldn't be hard to do. Take a GB of flash, structure it as a ring buffer. That eliminates the "small random writes" problem - you're just writing a linear journal, and the places you're writing are pre-erased and ready to go. If the power fails the drive just plays back the cache when the power comes back on.
That would let you have massive improvements in write performance. Metadata updates leave you seeking all over the disk. BTRFS is currently very slow to fsync because of this. But if it could just blast it to a big flash cache, and the drive could confirm that as committed to disk immediately, it'd scream.
Unfortunately all the manufacturers seem to just want to use it as a big persistent read cache to make Windows boot faster.
A hybrid drive would be great in my laptop. It doesn't have room for "storage" drives and a 600GB SSD would be heinously expensive. You could also put one in a USB 3.0 external enclosure (I assume they can work like that.) That would give you a nice trade off between speed, capacity and, most importantly, portability.
That seems to be what Seagate is thinking too. Since the drive is in the 2.5" form factor.
I have one. It works great, but "chirps" occasionally which I think is the sound of the motor spinning down. None of the firmware updates i've applied that claim to fix the chirp actually fix it.
It runs much faster than my previous drive, but i'm also comparing a 7200RPM drive to a 5400RPM drive so the speed increase isn't just because it's a hybrid.
I guess the advantage of the SSD cache is that if you use it in a circular fashion you can avoid a lot of the 'read-erase-rewrite' cycles... but I don't know how the cache is organised for sure.
There are only two things drive cache can help with significantly. When rebooting, where memory is empty, you can get memory primed with the most common parts of the OS faster if most of that data can be read from the SSD. Optimizers that reorder the boot files will get you much of the same benefit if they can be used.
Disk cache used for writes is extremely helpful, because it allows write combining and elevator sorting to improve random write workloads, making them closer to sequential. However, you have to be careful, because things sitting in those caches can be lost if the power fails. That can be a corruption issue on things that expect writes to really be on disk, such as databases. Putting some flash to cache those writes, with a supercapacitor to ensure all pending writes complete on shutdown, is a reasonable replacement for the classic approach: using a larger battery-backed power source to retain the cache across power loss or similar temporary failures. The risk with the old way is that the server will be off-line long enough for the battery to discharge. Hybrid drives should be able to flush to SSD just with their capacitor buffer, so you're consistent with the filesystem state, only a moment after the server powers down.
As for why read caching doesn't normally help, the operating system filesystem cache is giant compared to any size it might be. When OS memory is gigabytes and drive ones megabytes, you'll almost always be in a double-buffer situation: whatever is in the drive's cache will also still be in the OS's cache, and therefore never be requested. The only way you're likely to get any real benefit from the drive cache is if the drive does read-ahead. Then it might only return the blocks requested to the OS, while caching ones it happened to pass over anyway. If you then ask for those next, you get them at cache speeds. On Linux at least, this is also a futile effort; the OS read-ahead is also smarter than any of the drive logic, and it may very well ask for things in that order in the first place.
One relevant number for improving read speeds is command queue depth. You can get better throughput by ordering reads better, so they seek around the mechanical drive less. There's a latency issue here though--requests at the opposite edge can starve if the queue gets too big--so excessive tuning in that direction isn't useful either.
Hybrid drives, and even all of the hybrid RAID controllers I've looked at, only use the SSD for read acceleration. They aren't used for writes, from what I could tell from their specs. So you're almost certainly better off upgrading your system to the next larger amount of RAM rather than getting a hybrid drive.
Personally, I looked at my storage usage and realized that if I didn't keep *EVERYTHING* on my laptop (every photo I'd taken for 10+ years, 4 or 5 Linux ISOs, etc) and instead put those on a server at home, I could go from a 500GB spinning disc to an 80GB SSD. So I did and there's been no looking back. The first gen Intel X-25M drives had some performance issues, but since then I've been happy with the performance of them.
This Drive is CRAP
ASSUMING that it still only does read caching.
I bought one of the Gen-1 drives and was very underwhelmed. I wanted write caching; 4GB of non-volatile memory with the performance of SLC flash could allow windows (or whatever) to write to the drive flat out for up many seconds without a single choke due to the drive.
In addition 4G of write-back cache is enough to give a significant performance boost for continuous random writes across the drive and even more so across a small extent such as a database or a DotNET native image cache.
But for reading it's insignificant compared to the 3-16Gbytes of (so much faster) main memory that most systems contain, except at boot time when, unlike RAM, it will already contain some data. The problem with this is that it will contain the most recently read data, whereas the boot files can quite reasonably be described as least recently read.
So in the real world it's useless for anything except a machine that's rebooted every five minutes ...
That's horribly incorrect. I liked the sound of hybrid drives as well when I saw the price... The 500GB laptop hard drives with 4GB Flash for $150, should be awesome... But I, not being an idiot, did some research, and sure enough, the reviews say it's not remotely comparable to a real SSD.
eg. http://www.storagereview.com/seagate_momentus_xt_review
It's faster than a drive without such a cache, and it might be a good option for a laptop, but even there I'd say a 32GB SD card would be cheaper, and will work wonders on FreeBSD with ZFS configured for L2ARC...
I have no particular interest in what anyone buys, but the comparison to real SSDs is a massively dishonest.
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That's precisely what a hybrid HDD does, except it takes the decision regarding what will benefit most from going in the SSD out of your hands.
Crucial M4. Latest firmware update makes the drive about 40% faster and is non-destructive.
The article seems to think hybrid drives are the best of both worlds, but they are not.
They have the unknown reliability of SSD/flash drives (they do fail) COMBINED with the failure rate of consumer grade HD's (not that good).
They are not as speedy as pure SSD and not as cheap as pure HD.
So, the people that want speed, spend the money for a real SSD and use cheap reliable HD's for mass storage in a nas.
The people that want cheap, buy regular old HD's and accept the lower performance or just whine about it without doing anything about it because they are cheap.
The middle market, the people to cheap to buy a SSD but willing to spend far more on a small HD... I guess it just ain't there. ESPECIALLY since this lower class of consumer tends to buy ready made machines. Notice how the consoles only increase the HD space at the same time netbooks do? When THAT size of laptop HD as reached rock-bottom prize and you actually would have to pay more to get a smaller sized one?
Well, same for budget PC's makers. They buy HD's in bulk and put the same size in everything to cut costs. They are NOT going to add several tenners worth of hardware in the faint hope that budget PC buyers will buy their more expensive model when its sits next to the cheaper models in the shop.
And the high-end PC makers? They simply buy cheap SSD's and charge a premium for them.
Budget and high-end markets are FAR easier to supply for then the mid range. Because the budget people think anything more expensive is a rip-off and the high-end people look down their noses at anything cheap.
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You may solo them, I prefer them in a group.
and their upcoming Ivy Bridge chipset will take it even further. Both allow for the use of a small SSD drive as a cache against a larger traditional hard drive.
Per the wiki page on their chipsets, The Z68 also added support for transparently caching hard disk data onto solid-state drives (up to 64GB), a technology called Smart Response Technology
SRT link is http://en.wikipedia.org/wiki/Smart_Response_Technology
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So how do hybrid drives decide what's stored in the SSD vs the disk? From working in the hard drive business, I can think of several ways to tackle this - which is it?
1. Drive observes usage patterns and stores data on SSD vs disk based on that. This would be cool since it's transparent to the OS, etc., so it can work by "magic" (e.g. like bad block remapping), but it feels like it might be less effective than the other strategies depending on how good a job it does guessing how data is used. Also, there are some cases that are 'rare' (such as boot time) but which are important to optimize, even if statistically it wouldn't appear so.
2. Driver/OS controls what's stored where. This could be great, since they can have much more knowledge of what's going on than the drive.
3. SSD and disk are distinct 'drives'. This would allow the user to optimize (e.g. put boot OS and swap on SSD, big files on disk, etc.). But it requires users to understand and manage tradeoffs explicitly, which most people probably don't want to deal with.
So which is it? Does anyone know?
Enable 3D printed prosthetics!
it still requires 2 drives in the machine. for laptops this is often not viable.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
It sucks but has an easy but time consuming fix that leaves you with the drive contents intact:
Boot a live Linux distro. And hook a USB HDD to the system and mount it. The USB hdd can even be formatted NTFS if the live distro has FUSE installed along with the ntfs-3g driver, most live distros already have it or will allow you to install them. Assuming your SSD is the primary or only disk in your system then:
(You need to be root or use sudo, on most live distros you simply type "su root" or "sudo -s")
/dev/sda is the first disk in the system. you may have to run ls /dev/sd* to get a list of disks and partitions. and note, sda is the entire disk block-for-block, sda1 is a partition just like sda2 , sda3 etc. If you have more than one disk and don't know which letter it is then simply type fdisk -lu /dev/sdX (X being the letter you want to check) and it will dump the drive info.
It may take about 5+ hours assuming you have a 512GB SSD and an optimal USB transfer rate of 25MBps to the backup disk (in my experience the average for USB 2.0 write speeds). Faster backup disks and smaller capacity SSD's will backup much faster.
Once complete, you now have a bit for bit block-level copy of the SSD. This ignores the boot sector, boot loaders, partitions and file systems. It does not matter what OS you had on it, how many partitions or what file system you used. if your very paranoid and want to wait hours more, the run diff against the disk and disk image file to be sure they are an exact copy (never did it and never will).
Now reboot and upgrade the firmware the way the manufacturer tells you. So now your data is wiped out, big stinkin deal. Fire up the live Linux distro and again attach your backup disk and then enter the following command:
This writes the image file back to the SSD and if all goes well (It has never failed me yet and I have done this dozens of times for various systems) you now have your upgraded firmware with its original contents fully intact.
You can even mount one or more of the partitions contained within the disk image (under Linux of course) if you do a bit of homework (search google for mounting dd images) or just go here:http://darkdust.net/writings/diskimagesminihowto That tutorial is how I started playing with dd images.
You can also movethe contents of a smaller cramped disk to larger drives. Works for windows/NTFS too! You simply dd the entire smaller drive to the new drive (works best when both drives are hooked up via sata.) Then you use gparted or some other parted disk GUI to grow the file system on the new drive. Shut down and remove the linux cd/thumb-drive and remove the old disk and move the sata cable from the old disk to the new disk. Boot your PC and if your using windows (2000, XP , Vista, 7) it will run the check disk to verify the volume (DONT SKIP IT!) and reboot. Once it reboots to windows, open up explorer and see that you now magically have all that shiny new space without formatting, reinstalling, adding new drive letters or mounting drives under folders etc. Its transparent!
Example command:
sda is the small disk and sdb is the new large disk. I have done that trick multiple times as well with a 100% success rate. My friends were amazed.
Using ProfilesDirectory to redirect folders to a drive other than the system volume blocks upgrades. Using ProfilesDirectory to point to a directory that is not the system volume will block SKU upgrades and upgrades to future versions of Windows. For example if you use Windows Vista Home Premium with ProfilesDirectory set to D:\, you will not be able to upgrade to Windows Vista Ultimate or to the next version of Windows. The servicing stack does not handle cross-volume transactions, and it blocks upgrades.
http://support.microsoft.com/kb/949977
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But the SSD doesn't have to be added as a discrete component. You can already get motherboards that incorporate a small SSD drive to be used with SRT.
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