On Sun, Apr 17, 2011 at 10:59 AM, Phoenix <phoenix.kiula@gmail.com> wrote:
> TOP does not show much beyond "postmaster". How should I use TOP and
> what info can I give you? This is what it looks like:
We're basically looking to see if the postmaster process doing the
vacuuming or reindexing is stuck in a D state, which means it's
waiting on IO.
hot the c key while it's running and you should get a little more info
on which processes are what.
> 4799 postgres 15 0 532m 94m 93m D 0.7 1.2 0:00.14
> postmaster
That is likely the postmaster that is waiting on IO.
> VMSTAT 10 shows this:
>
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 3 14 99552 17900 41108 7201712 0 0 42 11 0 0 8 34 41 16
> 2 17 99552 16468 41628 7203012 0 0 1326 84 1437 154810 7 66 12 15
> 3 7 99476 16796 41056 7198976 0 0 1398 96 1453 156211 7 66 21 6
> 3 17 99476 17228 39132 7177240 0 0 1325 68 1529 156111 8 65 16 11
So, we're at 11 to 15% io wait. I'm gonna guess you have 8 cores /
threads in your CPUs, and 1/8th ot 100% is 12% so looks like you're
probably IO bound here. iostat tells us more:
> The results of "iostat -xd 10" is:
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
> avgrq-sz avgqu-sz await svctm %util
> sda 0.00 7.41 0.30 3.50 2.40 87.29 1.20 43.64
> 23.58 0.13 32.92 10.03 3.81
> sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
> 0.00 0.00 0.00 0.00 0.00
> sdc 0.00 18.32 158.26 4.10 2519.32 180.98 1259.66
> 90.49 16.63 13.04 79.91 6.17 100.11
100% IO utilization, so yea, it's likely that your sdc drive is your
bottleneck. Given our little data is actually moving through the sdc
drive, it's not very fast.
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
> 8GB memory in total. 1GB devoted to PGSQL during these operations.
> Otherwise, my settings are as follows (and yes I did make the vacuum
> settings more aggressive based on your email, which has had no
> apparent impact) --
Yeah, as it gets more aggressive it can use more of your IO bandwidth.
Since you
> What else can I share?
That's a lot of help. I'm assuming you're running software or
motherboard fake-raid on this RAID-1 set? I'd suggest buying a $500
or so battery backed caching RAID controller first, the improvements
in performance are huge with such a card. You might wanna try testing
the current RAID-1 set with bonnie++ to get an idea of how fast it is.