9940 A and B

[xxx01]

We've been using 9940A drives for some time now. Recently, we added a few B drives. Although the B drives are supposed to write faster, we are finding that they are writing at about the same speed as the A's do. We use multi-plexing of 4, compression at the tape drive. All else in the policies are the same for both drive types.

any ideas on what to look at?

 

[lenski]

try a test of multiplexing of 3/4/5 and see what the results are. Tuning is a bit of an art rather than science. Make small changes both ways and see what improves things. But as always you can have the fastes drives in the world but if you can't get the data to them you might as well have the slowest. Any tape can run faster than a disk. So sometimes a slow tape will be faster than a fast tape because it would not have to stop and wait for more data. The way to run tape drives is try and overload them.

 

[xxx01]

thanks lenski. i was thinking that it might have to do with buffers and such. why can't this stuff ever be resolved by just updating drivers or something. wishful thinking i guess.

 

[mjdes]

Also, try increasing your block size on the B drives.

 

[comtec17]

Also remember that your drives only push as fast as the slowest device on your system. This could be the NIC, SCSI adapter, HBA, switch, etc..

 

[xxx01]

mjdes, do you mean the "maximum fragment size" on the storage unit properties screen? or the buffer size on the media server?

comtec17, right now the media server has an hba, to a 2gb emc switch, to the drive. the media server receives data via gb nic with clients that have gb nics. i'm thinking the slowest thing here is the tape drive. ???