From: Noelle M. Vega (nmvega@computingarchitects.com)
Date: Fri Mar 02 2007 - 10:54:24 EST
Hello:
I will put a call into Veritas for this, but perhaps some on here may
have seen this.
We have multiple Oracle 10g databases running on the same
Solaris 8 (SPARC) box. The databases
are setup such that a main database
streams data to two other databases (implemented as part of the
Oracle 10g
Streams feature).
The filesystem type in use for these databases sit is "VxFS
v4.1".
====================
What we noticed is this:
====================
When the redo logs for these databases sit on a VxFS filesystem, there is
*constant* high read I/O associated
with them (the redo logs), even when there
is little-to-no application activity driving the database.
With average
service times (asvc_t) of 35 - 60 ms.
But when we move the redo logs to a UFS
filesystem, the read I/O drops dramatically - which is to say,
in line with
what we would expect (a few miliseconds or even less).
Although we do not
fully understand how Oracle streaming works, we suspect some sort of regular
scanning
activity to identify changes and maintain the replication between
databases. That said, perhaps there is
a mount option to VxFS, either present
or omitted, that is the cause of this problem on VxFS.
Those mount options,
as shown by "mount -p", are currently as follows:
rw,suid,delaylog,largefiles,qio,ioerror=mwdisable,dev=3a0bf68
(I have to
re-read the man page for mount_vxfs(1M))
Does anyone have any ideas as to
what is happening, mount options *and* otherwise. Note that I tried
tuning the
VxFS filesystems for larger read-aheads (via vxtunefs / tunefstab), but with
nominal improvement.
I also implemented increases to "vol_maxio" and "maxphys"
in /etc/system to align with the
underlying EMC disk stripe sizes (4mb), also
with nominal improvement.
TIA,
Noel Milton
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