On Tue, October 12, 2010 18:31, Bob Friesenhahn wrote:
> On Tue, 12 Oct 2010, Saxon, Will wrote:
>> Another article concerning Sandforce performance:
>>
>> http://www.anandtech.com/show/3667/6
>>
>> [...]
>>
>> When I read this I thought that it kind of eliminated Sandforce
>> drives from consideration as SLOG devices, which is a pity because
>> the OCZ Vertex 2 EX or Vertex 2 Pro SAS otherwise look like good
>> candidates.
>
> For obvious reasons, the SLOG is designed to write sequentially.
> Otherwise it would offer much less benefit. Maybe this random-write
> issue with Sandforce would not be a problem?
The other thing is that the article talks about an SF-1200-based drive.
And an MLC one to boot.
When SandForce originally came up on this list a while ago, I got the
general impression that while SF-1200-based devices were fine for L2ARC
caches, the consensus was that you would want an SF-1500-based devices for
slogs.
Not only does the SF-1500 get you better write IOps, the devices that used
them also tended to have batteries or super-caps as well. This helped with
data integrity in the case of unexpected power outages. SF-1500 units were
also usually available with SLC flash, which would help with longevity
give the write-oriented nature of slogs. See:
http://www.anandtech.com/show/3661/
So while the 'dedupe article' is informative, and the conclusions about
slogs and SF-1200-based devices appear sound, it's a bit beside the point
IMHO. Sadly there don't seem to be many SSDs out there that you /really/
want to use for slogs: there are many that you can make due with
(especially in mirrored configurations), but few that are ideal.
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