Yes, there is overhead on tape, but the tape drives will theoretically
write at rated write speed TIMES THE COMPRESSION RATIO.  I have seen a
sustained 60 MB/second into a 3590 tape drive.  It required high powered
hardware and significant tuning to get this rate.

Such high performance  is only attainable if the processor, disk,
ethernet, or ?? will also sustain this rate.  Performance is limited by
the slowest component.

Your parity of performance between disk and tape storage pools does not
surprise me.  Something other than the disk or tape is constraining your
system.  The rate you are seeing will give the first hint as to that
bottleneck.



Orville L. Lantto
Datatrend Technologies, Inc.  (http://www.datatrend.com)
IBM Premier Business Partner
121 Cheshire Lane, Suite 700
Minnetonka, MN 55305
Email: Orville.Lantto AT datatrend DOT com





"Pearson, Dave" <DCPearson AT SNOPUD DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
07/24/02 01:31 PM
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Re: diskpool performance


ON Tape... It take time to unwind, take the tape out, put another tape in
then start processing...
With Diskpool.  Thre is non of this.

My thought
Dave Pearson


> -----Original Message-----
> From: Orville Lantto [SMTP:orville.lantto AT DTREND DOT COM]
> Sent: Wednesday, July 24, 2002 11:03 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: diskpool performance
>
> What are your throughput values?  Tape is not necessarily slower than
> disk, especially when the data is compressed on the tape drive.
>
> Orville L. Lantto
> Datatrend Technologies, Inc.  (http://www.datatrend.com)
> IBM Premier Business Partner
> 121 Cheshire Lane, Suite 700
> Minnetonka, MN 55305
> Email: Orville.Lantto AT datatrend DOT com
>
>
>
>
>
> Steve Freeman <sfreeman AT ACRLIMITED.CO DOT UK>
> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
> 07/24/02 11:00 AM
> Please respond to "ADSM: Dist Stor Manager"
>
>
>         To:     ADSM-L AT VM.MARIST DOT EDU
>         cc:
>         Subject:        diskpool performance
>
>
> Please could someone advise me on the following issue we have with tsm.
> I am a TSM novice and would appreciate some pointers etc.
>
> Environment :  TSM 4.2.0  AIX4.3.3 ML09 Server and Client on same Server
> using Sharedmem
>
> 2 Stgpools defined diskpool and tapepool
>
> we have created a diskpool on RAID5 and created random access volumes
> Total Diskpool size is 150GB. Our nextpool is tapepool for migration
> upon high thresholds being reached.
>
> We have compression turned off on the client  and set the selftune
> parameters in dsmserv.sys
> SELFTUNEBUF
> SELFTUNETXN
>
>
> Issue:  IF we initiate a client backup using sharedmem to the diskpool,
> it seems to take the same time as it does to backup the client straight
> to tapepool. I would have thought the diskpool access
> would be quicker ?
>
> The Diskpool is located on direct fibre attached storage with large
> read/write cache. The tapepool
> is SCSI attached ATL library with 2 drives
>
> Any suggestions or pointers to increase the throughput to a respectable
> level would be appreciated.
>
> kind regards
> steve freeman
> sfreeman AT acrlimited.co DOT uk