On Wed, Feb 19, 2014 at 8:13 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
> On Tue, Feb 18, 2014 at 2:41 PM, Tomas Vondra <tv@fuzzy.cz> wrote:
>> On 18.2.2014 02:23, KONDO Mitsumasa wrote:
>>> Hi,
>>>
>>> I don't have PERC H710 raid controller, but I think he would like to
>>> know raid striping/chunk size or read/write cache ratio in
>>> writeback-cache setting is the best. I'd like to know it, too:)
>>
>> We do have dozens of H710 controllers, but not with SSDs. I've been
>> unable to find reliable answers how it handles TRIM, and how that works
>> with wearout reporting (using SMART).
>
> AFAIK (I haven't looked for a few months), they don't support TRIM.
> The only hardware RAID vendor that has even basic TRIM support Intel
> and that's no accident; I have a theory that enterprise storage
> vendors are deliberately holding back SSD: SSD (at least, the newer,
> better ones) destroy the business model for "enterprise storage
> equipment" in a large percentage of applications. A 2u server with,
> say, 10 s3700 drives gives *far* superior performance to most SANs
> that cost under 100k$. For about 1/10th of the price.
>
> If you have a server that is i/o constrained as opposed to storage
> constrained (AKA: a database) hard drives make zero economic sense.
> If your vendor is jerking you around by charging large multiples of
> market rates for storage and/or disallowing drives that actually
> perform well in their storage gear, choose a new vendor. And consider
> using software raid.
You can also do the old trick of underprovisioning and / or
underutilizing all the space on SSDs. I.e. put 10 600GB SSDs under a
HW RAID controller in RAID-10, then only parititon out 1/2 the storage
you get from that. so you get 1.5TB os storage and the drives are
underutilized enough to have spare space.
Right now I'm testing on a machine with 2x Intel E5-2690s
(http://ark.intel.com/products/64596/intel-xeon-processor-e5-2690-20m-cache-2_90-ghz-8_00-gts-intel-qpi)
512GB RAM and 6x600GB Intel SSDs (not sure which ones) under a LSI
MegaRAID 9266. I'm able to crank out 6500 to 7200 TPS under pgbench on
a scale 1000 db at 8 to 60 clients on that machine. It's not cheap,
but storage wise it's WAY cheaper than most SANS and very fast.
pg_xlog is on a pair of non-descript SATA spinners btw.
