Re: New server: SSD/RAID recommendations?

On Thu, Jul 2, 2015 at 7:01 AM, Wes Vaske (wvaske) <wvaske(at)micron(dot)com>
wrote:

> What about a RAID controller? Are RAID controllers even available for
> PCI-Express SSD drives, or do we have to stick with SATA if we need a
> battery-backed RAID controller? Or is software RAID sufficient for SSD
> drives?
>
>
>
> Quite a few of the benefits of using a hardware RAID controller are
> irrelevant when using modern SSDs. The great random write performance of
> the drives means the cache on the controller is less useful and the drives
> you’re considering (Intel’s enterprise grade) will have full power
> protection for inflight data.
>
>
>
> In my own testing (CentOS 7/Postgres 9.4/128GB RAM/ 8x SSDs RAID5/10/0
> with mdadm vs hw controllers) I’ve found that the RAID controller is
> actually limiting performance compared to just using software RAID. In
> worst-case workloads I’m able to saturate the controller with 2 SATA drives.
>
>
>
> Another advantage in using mdadm is that it’ll properly pass TRIM to the
> drive. You’ll need to test whether “discard” in your fstab will have a
> negative impact on performance but being able to run “fstrim” occasionally
> will definitely help performance in the long run.
>
>
>
> If you want another drive to consider you should look at the Micron
> M500DC. Full power protection for inflight data, same NAND as Intel uses in
> their drives, good mixed workload performance. (I’m obviously a little
> biased, though ;-)
>

Thanks Wes. That's good advice. I've always liked mdadm and how well RAID
is supported by Linux, and mostly used a controller for the cache and BBU.

I'll definitely check out your product. Can you point me to any benchmarks,
both on performance and lifetime?

Craig

>
> *Wes Vaske *| Senior Storage Solutions Engineer
>
> Micron Technology
>
> 101 West Louis Henna Blvd, Suite 210 | Austin, TX 78728
>
>
>
> *From:* pgsql-performance-owner(at)postgresql(dot)org [mailto:
> pgsql-performance-owner(at)postgresql(dot)org] *On Behalf Of *Andreas Joseph
> Krogh
> *Sent:* Wednesday, July 01, 2015 6:56 PM
> *To:* pgsql-performance(at)postgresql(dot)org
> *Subject:* Re: [PERFORM] New server: SSD/RAID recommendations?
>
>
>
> På torsdag 02. juli 2015 kl. 01:06:57, skrev Craig James <
> cjames(at)emolecules(dot)com>:
>
> We're buying a new server in the near future to replace an aging system.
> I'd appreciate advice on the best SSD devices and RAID controller cards
> available today.
>
>
>
> The database is about 750 GB. This is a "warehouse" server. We load
> supplier catalogs throughout a typical work week, then on the weekend
> (after Q/A), integrate the new supplier catalogs into our customer-visible
> "store", which is then copied to a production server where customers see
> it. So the load is mostly data loading, and essentially no OLTP. Typically
> there are fewer than a dozen connections to Postgres.
>
>
>
> Linux 2.6.32
>
> Postgres 9.3
>
> Hardware:
>
> 2 x INTEL WESTMERE 4C XEON 2.40GHZ
>
> 12GB DDR3 ECC 1333MHz
>
> 3WARE 9650SE-12ML with BBU
>
> 12 x 1TB Hitachi 7200RPM SATA disks
>
> RAID 1 (2 disks)
>
> Linux partition
>
> Swap partition
>
> pg_xlog partition
>
> RAID 10 (8 disks)
>
> Postgres database partition
>
>
>
> We get 5000-7000 TPS from pgbench on this system.
>
>
>
> The new system will have at least as many CPUs, and probably a lot more
> memory (196 GB). The database hasn't reached 1TB yet, but we'd like room to
> grow, so we'd like a 2TB file system for Postgres. We'll start with the
> latest versions of Linux and Postgres.
>
>
>
> Intel's products have always received good reports in this forum. Is that
> still the best recommendation? Or are there good alternatives that are
> price competitive?
>
>
>
> What about a RAID controller? Are RAID controllers even available for
> PCI-Express SSD drives, or do we have to stick with SATA if we need a
> battery-backed RAID controller? Or is software RAID sufficient for SSD
> drives?
>
>
>
> Are spinning disks still a good choice for the pg_xlog partition and OS?
> Is there any reason to get spinning disks at all, or is it better/simpler
> to just put everything on SSD drives?
>
>
>
> Thanks in advance for your advice!
>
>
>
>
>
> Depends on you SSD-drives, but today's enterprise-grade SSD disks can
> handle pg_xlog just fine. So I'd go full SSD, unless you have many BLOBs in
> pg_largeobject, then move that to a separate tablespace with
> "archive-grade"-disks (spinning disks).
>
>
>
> --
>
> *Andreas Joseph Krogh*
>
> CTO / Partner - Visena AS
>
> Mobile: +47 909 56 963
>
> andreas(at)visena(dot)com
>
> www.visena.com
>
> <https://www.visena.com>
>
>
>

--
---------------------------------
Craig A. James
Chief Technology Officer
eMolecules, Inc.
---------------------------------