Compression lost on SAN-attached tape library

[JakeCutter]

I'm running ARCserve 2000 SP4 on a SAN-attached W2K server, to which is connected a Compaq ESL9198DLX library with 4 Compaq DLT8000 40/80 tape drives.

Also attached to the SAN and backed up as clients are 4 W2K servers, each with a copy of ARCserve 2000 SP4, SAN agents, Tape Library Options, the whole nine yards.

There is a properly-defined primary member on the SAN.

Last Friday I had to reinstall ARCserve on the primary due to insurmountable database issues. Once I completed the reinstallation and reapplied the SP and agents, I set up my backup and watched it kick off.

However, this morning the job was still running, looking for additional blank tapes, and we could see that it was no longer using compression. I've done the CA thing about loading a blank tape into a drive, but the options to compress, retension, etc., remain greyed out.

If anyone has seen this before or has any ideas, I'd appreciate it...



Jake Cutter
IT Operations: Always outnumbered, always outgunned...

 

[TudorP]

How do you know that the compression is off? Is it just because its asking for blank medias or did you check the SCSI log for the Mode Select?
I am asking because I think there is something else going on - for example you might be running full backups instead of incremental / diff etc?
HTH
Cheers TP

 

[JakeCutter]

TP,

No, it's definitely a compression issue - if I highlight the tape drives in Device Manager I can see that compression is off. I presume that means hardware compression, because I don't use software compression in my backup jobs. However, the option to change compression is greyed out.

And of course, instead of 80GB per tape I'm only getting 40GB...

Jake

Jake Cutter
IT Operations: Always outnumbered, always outgunned...

 

[TudorP]

OK - here is the thing. The hardware compression option is only available for stand alone drives. When the drives are in a library, AS will automatically set the compression ON when the tape engine starts. You can check that by looking in the tape log at the beginning where you will see a Mode Sense command for each drive. If any drive has the compression OFF, you will also see a Mode Select going by.
However, if your library contains any formatted tapes that have been written to with compression OFF, AS will turn the drive compression OFF in order to read (and subsequently append) to that tape. What you need to do is look at the properties of the tapes that only have 40G. Most likely you will see that the compression is off. Identify all the tapes that have compression OFF and as soon as the data on them is irrelevant, erase them. If you keep appending to them, when they will span with compression OFF.
I am not sure how or why the first tapes were written with compression OFF. This can happen in Cross Platform SAN environments, but I dont think that is your case. You might want to keep an eye on your tape log next time you start the tape engine - make sure you do not see any Illegal Requests when AS is trying to set the hardware compression...
cheers
TP

 

[JakeCutter]

TP,

Thanks for that - the ARCserve documentation seems incomplete on this subject...

I'll probably be rebooting the server later so I'll be watching it closely to see what happens. At the moment my log files are recording SCSI errors that restarting the ARCserve engines hasn't fixed, so my Server Administrator will probably go for a reboot.

I'll post again when it's back on the air...



Jake Cutter
IT Operations: Always outnumbered, always outgunned...

 

[jcsanchez]

Hello Jake,

I am having exactly the same problem. Did you fix it?. How?.

Thanks.