Re: Best Linux filesystem for Postgres data store ?

Steve Francis <sfrancis@xxxxxxxxxxxxxxxx> · Wed, 01 Dec 2010 08:05:47 -0800

    On 12/1/2010 7:54 AM, Kevin Grittner wrote:

Your RAID configuration and controllers will likely make a bigger
difference than your filesystem choices.  Be sure to get good RAID
controllers with battery-backed (BBU) cache, configured for
write-back.

    I agree that storage makes a bigger difference than filesystems in
    most cases.

    Just wanted to jump in and say that testing with your workload is
    really the only way to know things for sure. (Obviously, more
    spindles implies more IOps, more cache implies faster writes...)

    But I have seen cases where a dell PERC RAID controller (not sure
    that qualifies as "good") slowed things down when configured for
    writeback with a write heavy workload. We noticed very spiky disk IO
    rates on some database servers (we are monitoring company, so have
    lots and lots of pretty graphs.)  The controller seemed to accept a
    bunch of writes quickly, then when full then try to pump them all to
    disk, which took a non-trivial number of seconds. So we'd see the
    interesting state of iostat reporting zero disk transactions per
    second, but busy time = 100% and service time being hundreds of
    millseconds.

    Switching to write through made things much faster overall. Not what
    I expected.

    This was a PERC 5, so a few years ago. No doubt things have
    improved, but the point is to test and monitor.

    -- 

               Steve Francis

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