Re: New server: SSD/RAID recommendations?

As I have warned elsewhere,

The M500/M550 from $SOME_COMPANY is NOT SUITABLE for postgres unless you have a RAID controller with BBU to protect yourself.
The M500/M550 are NOT plug-pull safe despite the 'power loss protection' claimed on the packaging. Not all fsync'd data is preserved in the event of a power loss, which completely undermines postgres's sanity.

I would be extremely skeptical about the M500DC given the name and manufacturer.

I went to quite a lot of trouble to provide $SOME_COMPANYs engineers with the full details of this fault after extensive testing (we have e.g. 20-25 of these disks) on multiple machines and controllers, at their request. Result: they stopped replying to me, and soon after I saw their PR reps talking about how 'power loss protection isn't about protecting all data during a power loss'.

The only safe way to use an M500/M550 with postgres is:

a) disable the disk cache, which will cripple performance to about 3-5% of normal.
b) use a battery backed or cap-backed RAID controller, which will generally hurt performance, by limiting you to the peak performance of the flash on the raid controller.

If you are buying such a drive, I strongly recommend buying only one and doing extensive plug pull testing before commiting to several.
For myself, my time is valuable enough that it will be cheaper to buy intel in future.

Graeme.

On 07 Jul 2015, at 15:12, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:

> On Thu, Jul 2, 2015 at 1:00 PM, Wes Vaske (wvaske) <wvaske(at)micron(dot)com> wrote:
> Storage Review has a pretty good process and reviewed the M500DC when it released last year. http://www.storagereview.com/micron_m500dc_enterprise_ssd_review
>
>
>
> The only database-specific info we have available are for Cassandra and MSSQL:
>
> http://www.micron.com/~/media/documents/products/technical-marketing-brief/cassandra_and_m500dc_enterprise_ssd_tech_brief.pdf
>
> http://www.micron.com/~/media/documents/products/technical-marketing-brief/sql_server_2014_and_m500dc_raid_configuration_tech_brief.pdf
>
>
>
> (some of that info might be relevant)
>
>
>
> In terms of endurance, the M500DC is rated to 2 Drive Writes Per Day (DWPD) for 5-years. For comparison:
>
> Micron M500DC (20nm) – 2 DWPD
>
> Intel S3500 (20nm) – 0.3 DWPD
>
> Intel S3510 (16nm) – 0.3 DWPD
>
> Intel S3710 (20nm) – 10 DWPD
>
>
>
> They’re all great drives, the question is how write-intensive is the workload.
>
>
>
>
> Intel added a new product, the 3610, that is rated for 3 DWPD. Pricing looks to be around 1.20$/GB.
>
> merlin