Conko, Steven wrote:

why does having the diskpool in between improve performance?

The latency is lower on writing to disk when you aren't writing at the
same speed as the media. If you're writing to a tape slower than the
tape can process it, you have to stop/start the media all the time.
Wheras with a disk, (Ignoring buffering), you just have to wait for the
blocks to come round again under the write heads... (Yes, and you
normally buffer a lot more on a disk than to tape as well, but even when
buffering the tape, you still have to get the tape up to speed again to
write to it, so you'd need way way more buffer space for a tape).

IMO this is THE biggest advantage TSM has above & beyond products like
Legato.

H

-----Original Message-----
From: Alexander Lazarevich [mailto:alazarev AT HERA.ITG.UIUC DOT EDU]
Sent: Wednesday, October 30, 2002 4:35 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Multiple sessions per tape


Totally. We used to backup to tape. But since putting a disk spool
inbetween, the performance has significantly improved.

Alex
---                                                        ---
  Alex Lazarevich | Systems | Imaging Technology Group
  alazarev AT itg.uiuc DOT edu | (217)244-1565 | www.itg.uiuc.edu
---                                                        ---


On Wed, 30 Oct 2002, Joshua Bassi wrote:

It is restricted to one.  The best way to backup your data is to a disk
pool first, then bleed the diskpool to tape and you will get much better
performance out of your single session than you would if you backed up
directly to tape.


--
Joshua S. Bassi
IBM Certified - AIX 4/5L, SAN, Shark
Tivoli Certified Consultant - ADSM/TSM
eServer Systems Expert -pSeries HACMP

AIX, HACMP, Storage, TSM Consultant
Cell (831) 595-3962
jbassi AT ihwy DOT com


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Conko, Steven
Sent: Wednesday, October 30, 2002 10:16 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Multiple sessions per tape

We're running ADSM 4.2 on AIX 4.3.3, 3494 library, 3590 drives.

Is there any way to control the number of sessions per tape or is it
restricted to one?

Steven A. Conko
Senior Unix Systems Administrator
ADT Security Services, Inc.

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