On Thu, Jul 2, 2015 at 7:01 AM, Wes Vaske (wvaske) <wva...@micron.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-ow...@postgresql.org [mailto: > pgsql-performance-ow...@postgresql.org] *On Behalf Of *Andreas Joseph > Krogh > *Sent:* Wednesday, July 01, 2015 6:56 PM > *To:* pgsql-performance@postgresql.org > *Subject:* Re: [PERFORM] New server: SSD/RAID recommendations? > > > > På torsdag 02. juli 2015 kl. 01:06:57, skrev Craig James < > cja...@emolecules.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 > > andr...@visena.com > > www.visena.com > > <https://www.visena.com> > > > -- --------------------------------- Craig A. James Chief Technology Officer eMolecules, Inc. ---------------------------------