SFHA 6.1: Poor performance with VxFS
Hallo @all
I'm facing poor performance with VxFS ( EMC LUNs, host-based-mirrored volume with logplex ):
We compress and uncompress a 10GB file and here are the results:
pri620[root]/database/sybase_backup {NSH}: time compress test_a
real 1m43.920s
user 1m8.303s
sys 0m14.824s
pri620[root]/database/sybase_backup {NSH}: time uncompress test_a.Z
real 3m29.777s
user 1m18.035s
sys 0m14.054s
Here the same but with two mirrored local disks and ZFS:
pri620[root]/install {NSH}: time compress test
real 1m29.672s
user 1m14.996s
sys 0m9.424s
pri620[root]/install {NSH}: time uncompress test.Z
real 1m27.838s
user 1m19.017s
sys 0m6.383s
Uncompressing is much faster!
When I create the 10GB file with mkfile I can see with iostat that
write performance is about 180-200 MB/s, but uncompressing
the file write performance is only about 55MB/s.
Hardware Oracle T5-2, server instance is a "Logical Domain"
I've read several documentation but I'm not able to get it faster on VxFS.
The only way it was faster is a special mount option:
mount -F vxfs -o tmplog,convosync=delay,mincache=tmpcache
But this seems to be very unsafe.
Any hints?
Regards,
Heinz
Hello Heinz,
What is your volume layout? Having mirrored array disks helps with redundancy so you can safely stripe LUNs together for better IO. Also the /tmplog mount option is a bit risky and is not the default. You can use other logging options but as you have noted performance will take a hit.
If your volume is small you might need to check the block size. Using an 8K block size will perform better for most workloads.
I suggest taking a quick look at this article http://www.symantec.com/docs/TECH202712 . It will help you go through the various things that affect VxFS/VxVM performance.
I've written a tuning guide that incorporates many of the tips from support articles, admin guides, etc. If you are interested in seeing it send me a message with your email. Thanks.