Re: Sudden drop in DBb performance

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On 09/05/2011 02:48 AM, Tomas Vondra wrote:
On 3 Září 2011, 9:26, Gerhard Wohlgenannt wrote:
Dear list,

we are encountering serious performance problems with our database.
Queries which took around 100ms or less last week now take several
seconds.

Results of Bonnie++

Version  1.96       ------Sequential Output------ --Sequential Input-
--Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
/sec %CP
voyager         95G  1400  93 27804   3 16324   2  2925  96 41636   3
374.9   4
Latency              7576us      233s      164s   15647us   13120ms
3302ms
Version  1.96       ------Sequential Create------ --------Random
Create--------
voyager             -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
                files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
/sec %CP
                   16   141   0 +++++ +++   146   0   157   0 +++++ +++
172   0
Latency              1020ms     128us    9148ms     598ms      37us
485ms


That seems a bit slow ... 27MB/s for writes and 41MB/s forreads is ait
slow with 8 drives.

Tomas



Agreed, that's really slow.  A single SATA drive will get 60 MB/s.  Did you run Bonnie while the VM's were up and running?

  root@host:~# vmstat
  procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
   r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
   0  0      0 308024 884812 40512932    0    0   464   168  353   92  4  2 84  9


Only one line?  That does not help much.  Can you run it as 'vmstat 2' and let it run while a few slow queries are performed?  Then paste all the lines?


-Andy

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