Slashdot Mirror
Hybrid Storage Solutions Compared
Vigile writes "While few would argue with the performance advantages of solid state drives, the relative cost compared to spindle-based disks still make them a luxury item. The promise of hybrid storage solutions is to combine the benefits of both — large capacities with standard drive technology and performance advantages of solid state. PC Perspective published an article comparing several different solutions that vary in their approach to hybrid storage. The OCZ RevoDrive Hybrid combines a standard 2.5-in drive with a PCI Express-based SSD that offers the best overall performance and largest cache size. Seagate's new Momentus XT 2.5-in solution embeds the cache on the PCB of the drive, allowing notebook users to install this solution easily. Finally, the Intel chipset-based caching option combines either a 2.5-in or mSATA SSD with a standard hard drive on either desktop or mobile platforms, allowing the most flexibility of any other hybrid solution. All three have advantages for specific consumers, though, and varying performance levels to go along with them."
Doesn't the disk fail if that SSD cache dies? Correct me if I'm wrong, but SSD technology still has a severely limited number of max writes.
To offset political mods, replace Flamebait with Insightful.
Facebook released, some time ago, their Flashcache solution. It works similar to ReadyBoost, et al, except it works on Linux, and "pairs" an SSD with a hard drive. Very useful.
http://www.facebook.com/note.php?note_id=388112370932
Seagate's new Momentus XT 2.5-in solution
Had a 500 GB version in my laptop since they came out last year (Summer I think) And yes, it's much faster than a typical 7200 rpm drive.
The best thing about a boolean is even if you are wrong, you are only off by a bit.
What I want is a filesystem that can use a partition of an SSD and a partition of a rotating magnetic disk. Metadata, directories and small files on the SSD, big files on the rotating disk.
This ought to be fairly simple - anyone fancy hacking ext4?
Why bother?
For the price of one of these you could buy a larger ssd and a larger hdd (shortages not widthstanding)
The time for hybrid drives has passed with ssd approaching $1 per gb.
Adaptec has a new technology called Hybrid RAID, which uses 50% SSD/50% HDD in RAID 1 or RAID 10. Reads are serviced by the SSD(s) only. It seems to me you might need to short-stroke the HDD in order to make this a reasonable approach.
Their new 6E series is very inexpensive for 6Gb SAS cached (128MB) hardware RAID; 6805E is (8 int. ports) is about $225 retail:
https://www.adaptec.com/en-us/products/controllers/hardware/sas/entry/sas-6805e
I'm no shill or fanboy; I just found this interesting and relevant.
Thank you, Edward Snowden.
"Arguments from authority are worthless." —Carl Sagan
Reading from SSD is insanely faster than reading from SAS. Writing to SSD is much slower. There is no way around that.
Those hybrids products are simply a futile tentative to come up with a cheap alternative to what is really needed: adding a decent cache on SSD controllers so the write buffer is big enough to mitigate the write penalty, and adding enough processing power to perform destaging properly.
This being said - if someone comes up with a way to read from SSD and write to SAS, then it's a winner... but the magic part that brings the written bit from the SAS to be read by the SSD is the million-dollar catch.
Until then, those hybrids are just a Fisher Price implementation of sub-volume tiering.
lucm, indeed.
You can purchase 24 GB of ram for less than $200 today. I would love to see a side by side performance and energy consumption comparison with someone who decided to spend their extra money on DRAM.
I suspect what you'll see is that after a day all read operations are resolved instantly from the OS disk cache without the performance and power hit of flash. If you have write intensive workloads the current crop of SSDs would not be for you anyway.
Yes, it is a godsend in a laptop where you're likely to be limited to 4GB or 8GB of RAM. I put a 500GB XT in my mid-2010 15" macbook pro about three months ago. The 8GB of cache is about 10% of the working space I'm likely to use while processing photos during one sitting. It helps a lot when working with RAW camera images and HDR compositing after shooting on location wherever.
The problem with most hybrid disks is the fact that they don't know about filesystems, they don't know about current working conditions of the rest of the system and they don't know of user and application preferences: they're working with a very limited set of data available to them and thus they can only base their operation on guesses of what is going to be needed next. The OCZ RevoDrive is the exception here in that it's actually two drives that are both accessible separately to the OS and/or applications if one doesn't install their caching software.
OS- and filesystem-agnostic system is always going to be somewhat limited so it would be beneficial if the rest of these hybrid systems also allowed the OS direct access to the flash so that the OS can optimize its behaviour accordingly. Like e.g. the user is reading several multi-gigabyte files, say, disc images for example; a OS- and filesystem-agnostic hybrid will start caching those files since it doesn't know how large those files are or how often they're needed, whereas if OS handled the caching it could determine that those files are accessed very rarely, usually in large sequences, and thus it would be better to skip caching them and instead save the cache for any related smaller files that are accessed more often. If you're familiar with the Windows ReadyBoost it actually works similarly: it skips caching large files as usually mechanical drives are more than fast enough for large sequential reads, but it instead caches a helluva lot of all kinds of small files since flash is absolutely terrific at random accesses and reading in even hundreds of small files from a slow flash is still faster than reading them in from the fastest mechanical one (I have a class10 16GB SD-card in my laptop as ReadyBoost drive and I've certainly noticed huge improvement in application startup times)
So yeah, sure, do create hybrids, they're a good idea in general. Just allow the OS to flip a bit and gain direct access to the flash part, too, for those OSes that are aware of such.
A mid-2010 macbook is limited to 4-8 GB RAM? I could install 8 GB in my nearly five year old ThinkPad X61 tablet.
for some reason I thought this article may have been about Prius's or wind/solar power, but.....
There was an unknown error in the submission.
Putting both in the same can is the wrong way to do it.
A better way is to have SSD and hard disk as tiered storage. The OS is more likely to be able to make better decisions for what to store where. So think in terms of overmounting the SSD onto the HD file system.
The OS on reading a file from the HD looks at the access pattern and if it gets accessed frequently, it writes it out to the SDD. If a file hasn't been accessed for a while it gets deleted from the SSD if it's clean, written to the HD and deleted if it's dirty.
When a file is created it's written to the SSD. If it's not accessed for X hours, it's flushed to HD. If it's not accessed for Y hours (Y>X) it's deleted from HD.
With separate SSD/HD you can pick your components. You can also do things like mirror your SSD and RAID your HDs.
Surprised this sort of FS access not available on Linux/BSD yet.
Third Career: Tree Farmer Second Career: Computer Geek First Career: Teacher, Outdoor Instructor, Photographer.
I just built a system with this motherboard, and while I haven't run any benchmarks, it does seem to be very fast.
When someone says, "Any fool can see