Sybase performance

Kruchkoff, A Alex Alex.Kruchkoff at SYD.RABOBANK.COM
Tue Oct 23 02:17:29 EDT 2001


Hi

we have a sun e450 with 64-bits solaris 8 and sun StorEdge SRC/P Intelligent
SCSI RAID controller with disks which are configured as RAID 1+0.

DBA use Sybase and they want to have a lot of small raw devices. 
The limitation of Solaris is 8 partitions per disk.
If I allocate 8 small (1 Gb) raw devices I would not be able to access the
rest of the disk.
Solaris 8 has a loopback file system: a character/block device could be
associated with the file. 
I can mount a filesystem with `forcedirectio' and build the loopback devices
for files located on that filesystem.
And use that lofi devices for Sybase DB.

When I have more than 30 lofi devices the performance of Sybase is
decreasing:
top shows 49.7% idle 22.7% user 27.6% kernel 0.0% iowait 0.0%swap 
My question is: will the performance of Sybase increase if I'll use veritas
volume manager?

(A few weeks ago we did some testing: we allocated small raw devices under
veritas and lofi and did simple dd testing.
Reading/Writing a lofi device was faster than reading/writing similar size
veritas device 2 boxes were identical, same raid 1+0. But for testing we use
1 raw device only, not 35).

And another question: what are other advantages of the veritas volume
manager?
We don't need to use mirroring (RAID controller does mirroring, striping,
hot spare).

Thanks, I will summarise.

Alex

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