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I have a bunch of servers with very heavy I/O that currently use SATA3/SAS drives, but do suffer from I/O wait on the SATA drives, and I have just been alerted to the existence of SSHDs which cost the same for 1TB as the 1TB SATA drives that we currently use. However, previously (until Seagate shipped their first 3.5" SSHD in March) they seemed to be exclusively for Netbooks/Notebooks, which leads me to suspect they're not exactly built for the heavy I/O they'd be in for with my servers.

So, would an SSHD give me a performance boost over my SATA3 drives in a heavy I/O environment (such as multiple very large high speed file transfers) or is it best to stick with SATA3 with I/O wait??

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I think the real question is: Are you willing to use consumer drives in your servers? –  AthomSfere Jun 29 '13 at 22:06
    
No, the question is more or less would it be sensible to use SSHD rather than SATA3 on a production server? Regardless of the fact that SSHDs are consumer drives, if it is sensible to use them in a heavy production environment, I'd go for it. –  Seb Jun 29 '13 at 22:13
    
There's other factors tho - the serverfault guys (who do know their server stuff), would probably ask if its supported. Some of the other ones would suggest using PCIe SSds. –  Journeyman Geek Jun 30 '13 at 0:30
    
Ooh, PCIe SSDs look awesome, the servers have "Two PCI-Express expansion slots: (1) full-length, full-height slot; (1) low-profile slot (optional PCIx riser supported)", I'm not sure if that would let me have one or two PCIe SSDs. I guess I'll give it a go :P –  Seb Jun 30 '13 at 19:30

3 Answers 3

up vote 3 down vote accepted

This depends highly on your workload. The Hybrid drives you speak of generally only have about 8GB of SSD on them - If you're reading and writing the same ~8GB of data over and over again, then you'll see SSD performance. If you're doing large transfers where the data is read just once or twice (like with video / media servers), then you'll have better luck beefing up your platter storage because of frequent cache misses.

SSHDs are great for desktop users (Given 5TB of read requests on my system, 97% is of the same 32GB), but file servers tend to not have the same usage patterns.


If you have a mixed load of large sequential reads/writes and lots of random I/O on top of that, then I suggest you look at ZFS and use proper platter disks and a good SSD.

For reference, I recently set up a 5x4TB RAID array using ZFS, and it can go toe-to-toe with an SSD for sequential I/O (avg. 450MB/s sequential read on a 10GB file). This is further backed by an SSD as both a write/read cache, which in theory could give between 900MB/s and 1GB/s if half the workload is from cache and half is from platters. It is in effect the same thing as a very large SSHD, but you can customize and build it with enterprise-grade hardware, and easily replace individual parts when they fail.

Note: If you're using an SSD as a write cache, you should use two separate SSDs as a mirrored write cache so that you don't lose data when one fails. You can very easily take two 256GB SSDs, use 6GB from each as a mirrored write cache, and then use the remaining 500GB as a large read cache.

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So I'd be better off using RAID 0 with multiple SATA3 drives (with ZFS)? I do have a lot of random I/O with large sequential read/write. At the moment I use 1 OCZ and the RAM for the I/O cache –  Seb Jun 29 '13 at 22:25
    
Yeah. You can set up the RAID / caching yourself and use any file system, I simply recommend ZFS because it handles the RAID and the caching and it can guarantee integrity in the wake of power failure and silent corruption (RAID does not). SATA3 drives are the best way to handle large sequential R/W, and the caching helps to trap the random I/O from interfering with the SATA3 drives too much. –  Darth Android Jun 29 '13 at 23:51

A server with (8) intel 800 GB SSD's (DC S3700) using RAID 6 would be pretty sweet. Giving you a whopping 4800 GB with a fault tolerance of 2-drive fails would make me confident...So, yeah, I'd use SSD's on a server, but only with RAID 6. Wise? Smart people make dumb choices everyday...it's only about money!

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In short If your file cache is smaller than the ssd cache in hybrid drive, I am afraid your server won't be benefit from SSHD/hybrid drive.

There is a file cache handle by your operating system and keep files to prevent reading from disk again. If it may handle more than the size of your ssd cache in hybrid drive, what you need to access is already in file cache.

Check the size of file cache Linux command free or task manager in Windows.

There are some different from what they keep File cache and software-based hybrid handle files while firmware-based hybrid drive handles track-sector. The software-based keep the whole file even you just need to read only part of it while the firmware only keep data it is assigned to read.

Formula Given x as the variable for ssd cache size of a hybrid drive and y as the variable for file cache of the operating systems accessing the hybrid drive. the system shall be benefit from a hybrid drive when x is bigger than y.

More detail Size matter at Buffer and Cache in Hard Drive and Operating System explains the SSD Cache Size of your SSHD

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