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user41679
Asked: 2010-04-29 02:40:49 +0800 CST

Which upgrade path for disk IO bound postgres server?

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We currently have a Sun x4270 with 2xquad core Xeon Nehalmen 2.93ghz cores (16 threads), 72 gig of ram and 16 x 10k SAS disks split between the os raid 1, a partition for the Write Ahead Logs which is raid 10 and a partition for the database tables and indexes which is also raid 10, all xfs.

I'm currently evaluating which path to go down in terms of upgrades. We'll be sharding the DB at some point soon, but for now I need to focus on hardware upgrades specifically. The machine is not CPU or memory bound at all at the moment, just IOWait is become an issue. The machine is mostly write access as we have a heavy caching layer. We're seeing about 300 write IOPS average on both the database partitions.

We don't have any additional storage infrastructure like a Fiber Channel or ISCSI network.

Budget isn't too much of a concern, something inline with the size of this server (i.e no $1m IBM machines)

Space is ok on the DB side of things, we're running out obviously but there's also some reduction we can do. Additional space would be good though.

My current thoughts are either:

  • ISCSI SAN, possible with 10Gbit network that has solid state acceleration.
  • FusionIO card / Sun F20 card (will the FusionIO card work in the Sun box?
  • DAS shelf (something like this http://www.broadberry.co.uk/das-direct-attached-storage-servers/cyberstore-224s-das) which a combination of 15k sas disks and some Intel X25-E drives for DB indexes etc) what would I need to put in the x4270 to add a DAS shelf? I think it's a SAS HBA card, do I have to use Sun's own card or will any PCI Express card work?

Anything else??? what would you guys do from your experience?

I appreciate it's a lot of questions, but I haven't expanded a DB machine for a number of years and the landscape has changed dramatically since then! Any advice or feedback would be very much appreciated.

Let me know if there's anything else I can clarify.

Thanks in advance!

hardware hard-drive database postgresql

2 Answers

  1. Best Answer

    Something DAS cheaper:

    • Get a SuperMicro case - 2 rack units, 24 discs. THe brakdberry server you showed basically is one.
    • Supermicro sells a conversion kit for it to act as a DAS extension. Basically a "fake motherboard" (so the power supply starts) as well asthe cabling to get the SAS baclplane to the outside.
    • Plug in an Adapted controller - they are IIRC available from sun as rebranding. The 5xxx series has onewith 2 external SAS cables (PERFECT for the case mentioned before) and can handle 200 hard discs (did I say you can chain up the cases?).
    • Adaptec also supports using SSD as read cache, though mileage may wary ;) Try it out.

    Possibly the best solution you can get along.

    If you already have a SAS controllr (you indicate) it may well be an Adaptec one. Anyhow, in this cae you can just get the SUperMicro case in the mentioned extension configuration. No need to buy the complete server from broardberry, you gain nothing in performance.

    For discs, either go SAS 150 or look at the western digital velociraptors - they are a lot cheaper than SAS discs and have comparable IO load to a 10.000 RPM drive, especialyl with a powerfull controller.

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  2. flashcache can be something else to look at and possibly can be much cheaper than other options. look here for some tests.

    this blog post mentions interesting alternative hardware solution.

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