DLT 8000 thruput

[Richard A. Caisse_1]

using fbackup: 50 mins run time, 29341810 blocks written. Unless my calculations are all screwed up, this seems like half speed to me. The drive keeps changing from writing to idle. Compress light is on.

[Peter Kloetgen]

Hi Richard,

which block size do you use, perhaps you did a wrong calculation?


Peter

[harry d brown jr · Accepted solution]

Depending upon the type and speed of disks you are backing up will slow down backups. The speed of the backps will depend upon the speed and transfer rates of the disks, other system activity, and amount of data transfering to the tape drive. If the dlt tape drive goes idle, it has to backup to go forward again.


DLT 80i/e/r/m: 6 MB/s (21.6 GB/h) native, typically 12 MB/s (43.2 GB/h) with hardware data compression

Look at these two documents:

http://www.products.storage.hp.com/storage/pdf/dlt40_80.pdf

http://www.products.storage.hp.com/storage/pdf/smartpb5.pdf

live free or die
harry

[Richard A. Caisse_1]

I used the fbackup man page block size of 512.
It can't be 1024 because some of my backups are posting 117.5 mil. blocks which wouldn't fit on the tape.

[harry d brown jr]

Change the number of file reader processes from 2 to 6 to get better throughput so the taspe drive doesn't go idle.

live free or die
harry

[John Palmer]

You must specify a large blocksize (at least 64K) to get decent performance from the DLT8000 drive. See man fbackup and look for 'blocksperrecord'.

Quantum quote 6Mb/sec transfer rate but this is the rate that (compressed) data is written. It's difficult to know what compression ratio is actually being achieved by the drive and hence what the 'real' transfer rate is.

Regards,
John

[Richard A. Caisse_1]

Thanks to all. Your suggestions were very helpful running last nights tests and results excellent.