Your database is I/O-bound. You have, essentially, duplicated your
protection at different levels. You need to choose between 1) RAID-5 or
2) TSM Software mirroring, but you should not use both. Either one will
protect you from a disk drive failure, and either one will allow the
server to stay up and running when a failure occurs.

I believe that the best way is to use TSM Software mirroring on JBOD
(i.e. plain, raw) disk drives for the database and log, and RAID-5 for
the online disk storage pools. But if you are stuck using RAID-5 for
some reason, then do not use TSM Server mirroring as well; it is
redundant.

When you allocate your mirror copies, get the two copies as far away
from each other as possible. At minimum, they must be on separate
physical disk drives. Better to have them on separate I/O channels (SCSI
bus...). This separation will both help performance, and improve your
ability to continue running after a disk problem.

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu



On Tue, 22 Oct 2002, Raghu S wrote:

>Hi,
>
>There was a lot of discussion on this topic before.But i am requesting TSM
>gurus give their comments again.
>
>The set up is like this.
>
>TSM Server : Windows NT 4.0 SP6, TSM 5.1.0.0
>
>                            392 MB memory, P III
>
>                  Adaptech Ultra SCSI
>
>                Hard Disk :  Internal   Hardware RAID 5:
>
>                         array A : 8.678GB * 3 : 17.356GB data and 8.678 GB
>parity
>
>                         array B : 35.003 GB * 3 : 70.006GB data and 35.003
>GB parity.
>
>
>Both array A and array B are connected to the same channel.
>
>OS and TSM 5.1 are installed on array A
>
>TSM data base, recovery log and Disk storage pool are installed in array B.
>
>Database : 2GB+2GB = 4 GB  and mirrored at TSM level on the same array
>
>Recovery Log : 500MB + 500 MB = 1 GB and mirrored at TSM level on the same
>array
>
>Disk Storage pool : 10GB+10GB+10GB+10GB+5GB=45GB on array B
>
>
>TSM client: 4.1.2.12 ( Tivoli says 4.1.2.12 is not supported with 5.1
>Server. But i could take the backup,archive and restore with this
>combination )
>
>Number of Clients : 55, all are windows
>
>Incremental backup : 1GB/ client/day.
>
>backup window : 9AM to 6PM with 50% randamization ( all are in polling mode
>)
>
>LAN : 100Mbps
>
>End of the day only 10 clients could finish the backup.Remaining all are
>missing or "?" ( in progress ) or failed.
>
>Through the entire backup window the CPU load is 100% with dsmsvc.exe
>holding 98%
>
>I tested with various options. I stopped the schedular and fired 3 clients
>backup manually at the same time.Each client has 1 GB of incremental data.
>It took three hours to finish the backup. While backing up i observed there
>was lot of idletime outs of sessions.
>
>Network choke is not there. I checked this with FTP.
>
>Whats the bottleneck here? Is RAID 5 is creating problems ( DB,log and
>storage pool all are on the RAID 5 )? I asked the customer to arrange a
>testing machine without any RAID. I will be getting that in two days.Before
>going on to the testing i like to know your comments on this.
>
>
>
>Regards
>
>Raghu S Nivas
>Consultant - TSM
>DCM Data Systems Ltd
>New Delhi
>India.
>
>e-mail: raghu AT cosmos.dcmds.co DOT in,dearaghu AT rediffmail DOT com.
>