From: Erdei Tamás (Erdei.Tamas@kfki-lnx.hu)
Date: Fri Dec 09 2005 - 04:32:49 EST
Dear Managers,
I have to disk IO related questions, maybe some of you can help me:
1. Why is, that disk IO is extremly slow when I boot from the Solaris install
CD compared to the normal IO performance of the same hardware? I tested raw
read and write throughput with dd, and the result is, that using the CD booted
environment, the transfer rate is only 2 MByte/sec (according to iostat), and
when the system is running the normal installed OS environment, the rate is
about 8MByte/sec. Is the Solaris install CD kernel using different, some kind
of fail-safe drivers which result the poor IO? Is there a way to make the IO
faster using the CD environment? This might be critical when we would like to
do a system restore from tape backup...
2. We have a system with two external third-party SCSI disk enclosures (very
simple, just a power supply and SCSI connectors for the disks, no additional
hardware acceleration, RAID or anything). We installed two Sun branded HDDs
into one of the enclosures and two third-party disks into the other. We set up
SDS based RAID1 mirrors on both enclosures. Now the interesting thing is, that
the disk IO rate during a full mirror resync is about 7-8MBytes/sec on the Sun
disks and 55MBytes/sec on the third-party disks. And this is also reflected in
the resync times. Both the Sun and the third-party disks are new ones. Is it
possible, that Sun disks are so bad regarding performance? Do I have to throw
away the Sun disks and install third party ones into those servers where I am
running IO intensive applications to get the best performance?? This is really
strange.
Regards,
Tamas
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