Someone please settle this argument for me

[Jcage]

We run TSM on a mainframe. We have servers backing up to disc then migrated to tape as per the usual way TSM is set up.

Our capacity guy says we shouldn't BE writing to disk, everything should be going directly to tape. To me that defeats the whole purpose of TSM.

Any thoughts ?

 

[rore]

Hi,
What's the argument of the 'capacity' guy?

There is no usual way TSM is set up. The final setup depends on your needs and expectations in terms of backup AND restore performance, reliability and your resources availability. Other factors can influence the final setup as well.

Backing up to disk would be beneficial (but not limited to) to backup a big quantity of relative small clients or backing up file servers with lots of relatively small files. Random access method (disk) allows multiple backups (and/or sessions) running at the same time with good performance.

Backing up directly to tape would be beneficial (but not limited to) to big databases where big chunks of information can take advantage of your tape's sustained transfer rate, and SAN if available.

Rudy

 

[heada]

If you can stream and keep the tape drives busy, then write directly to tape (large DBs, etc) If you don't stream the data, write to disk and you wont get the problems with write, rewind, reposition, write, etc)

-Aaron

 

[ypcat]

Merry Christmas

It's always good to have a combination of disk and tape for many reasons. I tend to lean the opposite way where I want my nightly pools on disk, the primary storage (next tier) on disk as well, and then have the DR copy pool in the library as well as a 3rd database pool and an archive pool on tape.

If a database file being backed up is extremely large and you have the tape drives available (mount points) you may want to set a parameter to have only those large files streamed directly to tape.

The advantage of disk is the random access over the sequential access especially when it comes to the writes of inbound steams; you can have 50 clients writing to disk at the same time but if you have everything going to tape then you would need 50 tape drives/mount points to accommodate the demand.

It all depends on your setup as was said, but you should explore this.