TL891 TZ89 Drives and Throughput.

[Andrew Kumar]

Hello,

I have two TL891 mini libraries connected to an AHA-2944UW. The TL891 has two TZ89 drives (thus making it a TL892). I have seen reports that the TZ89 drives are capable of 5MB/Sec native (10MB/Sec with two drives) giving a total of 36 GB/hr

In my calculations 5MB/Sec should be 5*60 =300MB/Min and 300*60 = 18000MB/Hr (this is bytes).

I ran a backup of about 30GB and BackupExec 10 reported a speed of about 270MB/Hr. one of the figures is way of!!! The full backup and verify takes about 3.5hrs.

Either I have my B and b (bytes and bits) mixed up or have lost the plot.

Can someone please confirm what real world throughput I should get from the TZ89 drives as I am trying to find bottlenecks and though that the 100Mb network might be the bottleneck.

Actually the server DL380G2 (backup server with the TL891?s) is using load balancing on 2x100Mb NIC?s.

[Mark Poeschl_2]

Looks like Backup Exec's number is the "way off" one. If a backup AND verify of 30 GB is taking 3.5 hrs and you assume the time is spent equally on the backup and the verify, the backup takes 1.75 hours. 1.75 times your calculated rate of 18000 MB / hour comes out to 31.5 GB - pretty darnn close to the 30 you started with. I did find an old HP doc which quoted a throughput rate of 5 MB/sec for the DLT35/70 drive - which I think I remember equates to the TZ89.

[Cass Witkowski]

I haven't testing throughput with two drives and not on a Proliant. However, with one drive you get 5 MB/s in non compressed mode and ~ 9+ MB/s in compressed mode.

30 GB = 30,000 MB /3.5 Hrs
= 8,571.43 MB/Hr / 3,600 seconds/Hr
= 2.38 MB/second

Since this was backup and verify, the backup speed would be approximately double this
= 4.76 MB/second

It also sounds like you are backing up over the network so depending on the backup software there may be some serialization of the backup. Read a block off the source disk, send across the network, write to tape, read next block off disk.

You also have to take into account how fast the data is being read off of disk and is the source disk fragmented such that there are a lot of disk I/O's. This can really slow down the backup.