[Veritas-vx] striping on SAN disks for performance

[Cronin, John S.]

Certainly if using two arrays and four HBAs per server, software
striping across hardware striped LUNs could give a performance benefit.
Even in the more two HBAs per server and one array situation, striping
at the hardware level and then again at the hardware level could give a
performance benefit, particularly in the situation where the different
hardware striped LUNs were not using the striped across the same disks.
For sustained I/O, if you striped across enough disks (one way or the
other or both), eventually the bottleneck will be the HBAs.

On the big arrays, one other factor is the huge caches these things
have, and how they are mapped to the physical disks.  In some cases
using software to stripe again on LUNs that are striped in hardware may
show some performance benefit even if the LUNs are striped across the
same disks, if I understand things correctly (and I freely admit I may
not).

To stripe using software on Solaris, you either need to use Sun's
DiskSuite, or Veritas Volume Manager.  Also, in my experience Sun's UFS
is not particularly fast and you may see a performance benefit by using
Veritas VxFS.  I don't know enough about IBM's JFS to compare the
performance intelligently.

-- 
John Cronin
ipager: johncronin
Desk Phone: 404-986-3992
Cell Phone: 678-480-6266

-----Original Message-----
From: veritas-vx-admin at mailman.eng.auburn.edu
[mailto:veritas-vx-admin at mailman.eng.auburn.edu] On Behalf Of Miller
Alan
Sent: Thursday, February 26, 2004 3:46 PM
To: 'veritas-vx at mailman.eng.auburn.edu'
Cc: 'Jon Hudson'
Subject: RE: [Veritas-vx] striping on SAN disks for performance


Sorry, sent my response to early.

I wanted to say that my file systems range from 100 to 500GB. For
example, one SF15K Domain runs 2 SAP systems. Volume Group for 1st SAP
has 116 LUNS, 58 (16GB) LUNs each Shark Volume Group for 2nd SAP has 102
LUNs, 51 (16GB) LUNS each Shark.

The LUNs are seen on the Sun via 4 qlogic adapters, 2 separate HBAs per
Shark So each LUN has 2 paths(luxadm or vxdisk list, not sure which cmd
shows it)


--
Alan Miller	
is:energy  GmbH	
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