RE: storage service times

  • From: "Crisler, Jon" <Jon.Crisler@xxxxxxx>
  • To: <dannorris@xxxxxxxxxxxxx>, "Oracle L" <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 3 Jan 2008 14:12:32 -0500

A bit slower than I would expect, but not awful.  I think oracle
mentioned that service times above 10ms are a concern.   What about
async I/O, direct I/O settings ?  



From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Dan Norris
Sent: Thursday, January 03, 2008 12:51 PM
To: Oracle L
Subject: storage service times


I'm looking over a system that has what I believe to be a
much-larger-than-average service time for read and write I/O. 

Solaris SPARC
Hitachi (branded Sun 9990) storage array via 2xFC HBAs
8x 12 Gb storage array LUNs striped 256k stripe width using VxVM on the
host = about 90Gb volumes

Given that (somewhat incomplete) footprint, what are your first
"knee-jerk" reactions to these times for a 1-hour statspack report

                 Av      Av     Av                    Av        Buffer
Av Buf
         Reads Reads/s Rd(ms) Blks/Rd       Writes Writes/s      Waits
-------------- ------- ------ ------- ------------ -------- ----------
       397,958     111    8.3     1.0       79,676       22      4,114
       410,619     114    9.2     1.0        8,695        2    161,789
       159,094      44    8.3     1.0      137,040       38         31

These are rolled up to the tablespace level and I'm particularly
interested in comparing with other people's Av Rd(ms) (the 3rd col) and
Av Wt(ms) (the last col). I'll go gut feeling, based on past
experiences elsewhere, is that 6+ ms seems about 50-100% higher than I
expected to see. 

I know I'm getting service times from Oracle without offering any info
on what the OS or Vol Mgr say about the service times viewed from those
points of view, but the service time in the DB is the only metric that
matters at this point. I'll dig in to the other layers as necessary when
I start debugging. I'm looking for your opinion to see if this is a
problem or if I just set my expectations too high. :-)


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