Re: Balancing Disk Data Across Arms

[mcrump@xxxxxxxxxxxxxx]

Tom,

DSKBAL works fine but you probably won't get much benefit.  It is designed to
work at IPL time and balance the data (based on capacity) at that time.  If you
data is distributed properly for capacity purposes running DSKBAL won't do
anything.

If you could get to V4R4 the STRASPBAL command offers some neat advantages.  One
it can be done anytime (no IPL required) and two it has an option whereby you
can balance the data based on *USAGE which allows you to best spread your data
based on usage issues.  I've not used the *USAGE feature yet.  I have used the
*CAPACITY when we have added disks and it works fine.  Depending on your system
you may want to watch when you run it.......it could have a performance impact.
The larger your system and the more drives you have the less chance there is of
a negative impact.

I've included some documentation off of my system.  BTW, we did a V4R2 to V4R4
upgrade (4 systems on the same weekend) and had no issues...if that helps.

HTH

Mike

(See attached file: QSYSPR~1.TXT)



Has anyone used the DSKBAL command provided by IBM on a 4.2 system?
This function is available via PTF.

We run some accounting Monthend jobs that are heavy I/O.  When these
jobs run, other batch jobs slow down (other batch jobs are actively
running) and show I/O waits in  Performance Tools.

In the past year, we have added several disk drives to this system.
Generally, 1 or 2 at a time.  I believe what has happened is that since
these drives are empty when they are added, the IBM algorithm for
spreading data across arms actually fills these empty drives until the
percentage used is even again across all arms.  Thus, restoring or
copying files in production applications actually put this data on
these empty drives.  (timing)    I can see in performance tools that
during the Monthend process, 4 or 5 arms will exceed the guidelines for
the device.  These are the where the accounting data is located.

Without doing a full SAVSYS and RESTORE (option 21),  The Support Center
told me to install this PTF and use the DSKBAL command.

Any help would be greatly appreciated.

Thanks

Thomas A. Law Jr.

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