SUMMARY: Sybase performance

Sorry for the delay: we were doing some tests.

Thanks to Jeroen.Rijnbergen@seagate.com, andy.lee@orange.co.uk,
mahesh.hardikar@nl.fortisbank.com, and Darren Dunham [ddunham@taos.com]

Suggested solutions were:

1) don't use lofi devices, use files to which lofi devices pointed (fs
mounted with `forcedirectio')
2) use new feature from SDS 4.2.1 called `soft partitions' (to avoid the
Solaris limitation of 8 partitions per disk)
3) use VxVM.

TESTS.

ASE 12.5; 
5 db: 4110Mb; 4110Mb; 610Mb; 310Mb; 610Mb; pagesize - 2K.

1) using lofi devices pointing to files on the fs mounted with
forcedirectio: 2h 45m
2) using files on the fs mounted with forcedirectio: 2h 14m
3) using lofi as in 1) but splitting: 3 db on 1 disk and 2 db on another
disk: 1h 37m
3) using raw devices as disk slices (not acceptable: solaris 8 slices
limitation): 0h 36m
4) using raw devices as soft partitions (I applied the patch 108693-07): 0h
32m

I have not tested VxVM yet, but I will: I'm just preparing the environment.

*VxVM question* to the list: I know I can encapsulate the existing disk to
the Veritas,
but when I finish the test, How to de-encapsulate (restore) the disk which
is under control of VxVM?
(I know I can reformat the disk, make new fs and restore the data, but it's
a long way...)

thanks a lot.

rgds 
Alex

my original post:

-----Original Message-----
From: Kruchkoff, A (Alex) [mailto:Alex.Kruchkoff@SYD.RABOBANK.COM]
Sent: Tuesday, 23 October 2001 16:17
To: sunmanagers@sunmanagers.org
Subject: Sybase performance


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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