Re: Contemplating SSD Hardware RAID - Mailing list pgsql-performance

On 2011-06-21 08:33, Greg Smith wrote:
> On 06/20/2011 11:54 PM, Dan Harris wrote:
>
>> I'm exploring the combination of an Areca 1880ix-12 controller with
>> 6x OCZ Vertex 3 V3LT-25SAT3 2.5" 240GB SATA III drives in RAID-10.
>> Has anyone tried this combination?  What nasty surprise am I
>> overlooking here?
>
> You can expect database corruption the first time something unexpected
> interrupts the power to the server.  That's nasty, but it's not
> surprising--that's well documented as what happens when you run
> PostreSQL on hardware with this feature set.  You have to get a Vertex
> 3 Pro to get one of the reliable 3rd gen designs from them with a
> supercap.  (I don't think those are even out yet though)  We've had
> reports here of the earlier Vertex 2 Pro being fully stress tested and
> working out well.  I wouldn't even bother with a regular Vertex 3,
> because I don't see any reason to believe it could be reliable for
> database use, just like the Vertex 2 failed to work in that role.
>

I've tested both the Vertex 2, Vertex 2 Pro and Vertex 3. The vertex 3
pro is not yet available. The vertex 3 I tested with pgbench didn't
outperform the vertex 2 (yes, it was attached to a SATA III port). Also,
the vertex 3 didn't work in my designated system until a firmware
upgrade that came available ~2.5 months after I purchased it. The
support call I had with OCZ failed to mention it, and by pure
coincidende when I did some more testing at a later time, I ran the
firmware upgrade tool (that kind of hides which firmwares are available,
if any) and it did an update, after that it was compatible with the
designated motherboard.

Another disappointment was that after I had purchased the Vertex 3
drive, OCZ announced a max-iops vertex 3. Did that actually mean I
bought an inferior version? Talking about a bad out-of-the-box
experience. -1 ocz fan boy.

When putting such a SSD up for database use I'd only consider a vertex 2
pro (for the supercap), paired with another SSD of a different brand
with supercap (i.e. the recent intels). When this is done on a
motherboard with > 1 sata controller, you'd have controller redundancy
and can also survive single drive failures when a drive wears out.
Having two different SSD versions decreases the chance of both wearing
out the same time, and make you a bit more resilient against firmware
bugs. It would be great if there was yet another supercapped SSD brand,
with a modified md software raid that reads all three drives at once and
compares results, instead of the occasional check. If at least two
drives agree on the contents, return the data.

--
Yeb Havinga
http://www.mgrid.net/
Mastering Medical Data