update ( sync ) taking 20+ seconds to complete.

From: bboddy - Bill Boddy <BBODDY_at_acxiom.co.uk>
Date: Tue, 23 Mar 1999 13:17:15 +0000

Has anyone experienced the following:-

GS140 ( 8400 )with 6 x 625Mhz CPU's (EV56), with 6 x BA370's attached
via 2 pairs of HSZ70's running HSOF 7.0
Digital UNIX 4.0d with patch kit 3

Users complained recently that the server was running very slowly. On
examination , I noticed that the /sbin/update
process was at 95%+ for at least 20 seconds, then faded away then
kicked in at 95%+ again when update re-runs
sync ( as set , every 30 seconds ). I killed update ( when it was
sleeping ) and ran some sync's manually.
Each sync was taking about 20 seconds to complete.

I then did some dd'ing around various filesystems, to get a feel for
I/O performance. All I can say about this was
that I was getting some very inconsistent numbers back. Some
filesystems took about 2 seconds to copy a 25MB
File , and some filesystems were taking 15seconds+.

I then ran "defragment -vn" on all of the 28 advfs file domains. Seven
of them returned with some very strange figures.
See below.

 ONE OF THE GOOD ONES
defragment: Gathering data for domain 'hsz10d207'
  Current domain data:
    Extents: 305
    Files w/extents: 29
    Avg exts per file w/exts: 10.52
    Aggregate I/O perf: 98%
    Free space fragments: 51
                     <100K <1M <10M >10M
      Free space: 100% 0% 0% 0%
      Fragments: 36 2 7 6

ONE OF THE BAD ONES
defragment: Gathering data for domain 'hsz9d0'
  Current domain data:
    Extents: 4072
    Files w/extents: 1457
    Avg exts per file w/exts: 2.79
    Aggregate I/O perf: 100%
    Free space fragments: 3869
                     <100K <1M <10M >10M
      Free space: 2146867472848995% 4% 0% 311%
      Fragments: 3642 220 0 7

I then backed up one of the suspicious domains to another fresh volume
using vdump | vrestore,
and ran degragment -v on it.

After one hour it completed, and the results were still the same i.e.
...

                     <100K <1M <10M >10M
      Free space: 2146867472848995% 4% 0% 311%


I am now getting a bit stuck on what to do next.



Bill Boddy
UNIX System Administrator
Acxiom Ltd.
  0191 515 4348
 bboddy_at_acxiom.co.uk
Received on Tue Mar 23 1999 - 13:36:22 NZST

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