Rolling out flash in the enterprise? It's a matter of application Flash SSD is changing the way that we store data. Vendors would like you to use it for all of your applications – and you probably will at some point – but which applications does it make most sense for today, and which might you have to work a little harder on to justify its use? Some rarified high-performance applications …
No, they're not used for single byte IO. But take a DB app that's updating an account balance record; regardless of how large that record might be, that's just a few bytes of update. Add in RAID (or EC) and you're reading & writing a lot of disk blocks (4K on modern drives) just for that small update. SSD read/write units are much larger; the problem's exacerbated.
Hmmm. On the workstation front I was on the indirect receiving end of a numpty seller who was trying to tell their clients that there really wasn't much of a performance gain in using an SSD in a workstation compared to a HDD. Windows spends an inordinate amount of time reading and writing small chunks of data from arbitrary locations on a volume and this won't be improved through removing the mechanical action of forcing the damn drive head to move from one physical location to another. Repeatedly. Seriously?
While caches can be overloaded on an SSD but this is no real difference to HDDs which commonly suffer from cache overload situations that force the IO subsystem to wait. Not that storage systems couldn't or shouldn't be optimised for their intended purposes but for most operational situations an SSD is better than an HDD and the remaining cases are usual financially motivated rather than operational.
The author's comparison is only valid for sequential data, for which hard drives were never a bad solution in the first place. Where SSDs really shine is random data, since there's no physical motion involved for seeking. There, SSDs offer FAR more improvement for writes versus reads, because you can always using caching to help reads, but that doesn't work for writes (unless you have stable storage for a write cache)
Now that SSDs have become faster over the last few years they offer improvements in sequential I/O performance as well, but in an array where you can stripe across many drives you are generally limited by the controller and not the media so flash may not help.
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