Poor speed for LTO Backup

[Anthonyncm]

Dear all,

We have buy a Dell 128T LTO backup tape, same for HP C7200, in locally backup have 500M/min, but in network backup just drop down to 150M-220M/min, very poor speed, how can i incress the backup rates? Change the Block size?

Thanks
Anthony

[Alexander M. Ermes]

Hi there.
For network backup you should have your own net attached. If the net does not deliver enough data, the drive cannot get into streaming mode ( rewinding, positioning again and so on ).
That means, some more nics and a GOOD switch.
Rgds
Alexander M. Ermes

[Anthonyncm]

That's mean the bottleneck in the network.
If i try to setup the Fast Ethernet Channel to increass the Thoughput, can i solve this bottleneck?

Thanks
Anthony

[Angus Crome]

A reality check here guys;

500 Mb/min is only about 8 Mb/s (about half the rated throughput for LTO). You should be able to drive it a lot faster than this on direct attach and up around 10 Mb/s for a 100Base-T Full Duplex connection (better with a really good switch). I would look at your locally attached configuration first and see if there are any inconsistencies. "Any SCSI errors a really large SCSI cache (64/128Mb or larger) on a cacheing controller sometimes can cause reduced rates due to the streaming nature of tape data.

I would start by finding someone who has your configuration (someone on the Forums probably does) and see if they ran into similar problems).

As for the network, if you are getting that far below rated throughput, I would check the Auto-negotiation, duplex and speed configurations of all servers and the switch ports involved. Since auto-negotiation is notoriously flaky, I would recommend hard setting the configurations to the same settings on each server and its associated switch port.

[Anthonyncm]

Our server use 2 Xero CPU, 2G Ram, Parc 3/DC Raid Control,3pcs Seagate Ultra160 Harddisk run for Raid 5.
The backup larbary use the Adapter 39160 to connect.
I try to use PAT to check the network rates, just 1.9M - 2.5M/min.

Thanks
Anthony

[Jan Klier]

The one parameter in terms of performance to keep in mind is the speed at which data reach the drive.

For an LTO drive this rate needs to stay above 6MB/s in order to keep the drive streaming, which is critical for good performance.

[David Ruska]

As already mentioned, you need to make sure you can get data off your disks (and network) fast enough, and then you can optimize the tape drive side of things.

First, the tape drive should be on its own HBA (Ultra160).

Next, the backup application itself can make a big difference. NT backup on NT4 is quite slow, whereas on Win2000 it is considerably faster (but probably still not fast enough to stream Ultrium). Third party apps are generally faster than NT backup.

Third, tape block size makes a big difference -- 32K is the minimum recommended, but 64K or 128K would be better.

Forth, if tape capacity is not an issue, you could try turning off compression (HW & SW) to help keep the drive streaming.

Lastly, the larger the average file size, the better your backup performance will be.

Here's an Ultrium performance white paper that might help you out:

http://www.hp.com/products1/storage/products/tapebackup/ultrium_tapedrives/ultrium230/infolibrary/whitepapers/ultperfpress.pdf