Restore file from LTO

[gorally]

I just restore a 2 G file from the LTO tape. It took me over 7 hours to do it on a 100Mbp ethernet. There are no other backup/restore traffic going on the TSM server or the client. How would it take so long..does anyone has a branchmark how long is acceptable?



Thanks,

Ed

 

[sgabriel62]

You would think only 2 minutes maybe a bit longer if you have to wait for tape mounting.. Did you check the TSM and OS activity logs?



Steven

 

[gorally]

Tape mounting is not the bottle neck here. The fact is when I backup the file, I get the aggregate data transfer rate of 1,031kb/sec. When restoring the file, I only getting about 55kb/sec. I tried doing this excerise with various file size, range from 100Mb to 300 Mb. I got a rather consistent result. What kind of overhead does restoration have over backup?

 

[tom.s]

With a backup you are probably going to a diskpool. With a restore your are going from the tape pool. The difference may be between the pools rather than restore/backup. I know that with LTO there is some capability to slow the tape drives down, but is it possible that some kind of back-hitching is going on?



I would try restoring a file from your disk pool to the same client and see what the performance is like. Also try restoring the same file to the TSM server.



You might also want to take a look at what the session is doing to try and work out whether the client is waiting for the server or the other way around.

 

[may]

try also restoring the same file on an another server to see if there is a prblem on the server (Plateform, NIC configuration) or else....

 

[festradae]

Try to copy a file from the server to the client,if this take a long timethe problem is the network adapter,

 

[robin_sharpe]

Do you have tapealerts turned on? If not, you should... If you do, take a look in your activity log for tapealert messages regarding corrupted LTO cartridge memory (do a "q act search=corrupted begint=now-08:00"). There is a known problem with IBM LTO drives that was causing the cartridge memory to get corrupted... when that happens, the file search performance is adversely affected. That's really an undrstatement... we recently had to restore a couple of windows servers C: drives. Took about a week (yes a whole week!) to restore 4GB. Granted, the data was spread over about 300 tapes, but I observed tapes being mounted for 30 minutes or more before any data was transferred.



The real bad news is that you first need to upgrade your drive firmware to prevet further corruption. Then, to rebuild the corrupted memory, you have to read all the data on each affected cartridge. One way to do that would be a "move data" command for each cartridge. Another way is to use tapeutil or some similar program to read through each tape. Either way, it's pretty disruptuve. And the only way you will know what cartridges are affected is by reading them and seeing the tapealert message.



I haven't even attempted to fix our tapes yet, because StorageTek is not yet releasing the latest LTO2 firmware.



Good Luck!



Robin Sharpe

Berlex Labs