Is the disk pool cached?
I ran into a situation where the disk pool cache instead of tape was being used.
This slowed my LTO drives to a crawl during certain operations.
I now varyoff the disk pools before I run the process with expected results
Don't forget to vary them back on at the end..
Note: the disk pool cache is a great help in restore time, but it can adversely
the affect of what should be a tape to tape process.





Halvorsen Geirr Gulbrand <gehal AT WMDATA DOT COM> on 08/15/2002 03:00:23 AM

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

To:   ADSM-L AT VM.MARIST DOT EDU
cc:    (bcc: Joseph Pendergast/Corona/Watson)

Subject:  Bad performance from tape to tape



Hi All,
I have a performance problem when doing Space-Reclaamtion, or backup storage
pool, when TSM is copying data from one tape drive to the other.
Environment:
Windows 2K server, TSM 4.2.1.15.
Library, Compaq MSL5026, with 2 SDLT drives (Single Module Library).
SCSI Controller, Compaq 64-bit/66Mhz Dual Channel Wide Ultra3 SCSI Adapter
(Compaq version of Adaptec 39160)

Moving data from Disk to Tape runs with expected speed (8-10 MB/s).

>From Tape to tape speed is around 2MB/s. (50GB takes about 7-8hours.)

Does anyone know why? It is killing my daily operations.

Mvh
Geirr G. Halvorsen
TSM Enterprise Backup Specialist
WMdata Danmark A/S