topic Re: Compression problems with DAT40e & BackupExec in StoreEver Tape Storage

Compression problems with DAT40e & BackupExec

CA769052 — Wed, 27 Mar 2002 01:10:02 GMT

We have a DAT40e that is connected to a Novell Netware 5.0 server. It has been backing up fine for the past six months, but recently it has been reporting 'end of tape' and requesting a second tape to be inserted. Compression is enabled on the DAT40e (or at least I think it is with the number 2 configuration switch set to 'on') BackupExec compression is disabled. It appears to only be storing 15.9GB on this tape. I was expecting somewhere over 20GB with compression enabled. (right?) I'm not sure if the tape drive is actually compressing the data. Any recommendations?

Thanks in advance...

Robert

Re: Compression problems with DAT40e & BackupExec

CA756694 — Wed, 27 Mar 2002 13:49:00 GMT

Hmmm .. storing less data than the native amount, that is likely not to be anything to do with compression because a DAT40 should store 20GB native and anything up to 40GB with compression

It isn't anything obvious like you have been appending to a already full tape or using a shorter length media tape ??

How's the system performing; try running it
the performance assessment tool:

http://www.hp.com/support/pat

Has anything changed ?
Is it backing up the same type of data that it's always done or have you suddenly switched to something else ? Have you plugged more hardware onto the same SCSI bus ?? Is the tape device making lost of repositions ?

cheers,

John

Re: Compression problems with DAT40e & BackupExec

CA769052 — Wed, 27 Mar 2002 15:37:43 GMT

Actually, I'm using the smaller tape. 125mm, not the 150mm. Nothing on the hardware side has changed, but there has been a database added to the volume. The backup has increased a gig and a half. The tape won't hold over 15.9GB. (the total backup is 17.8GB) It displays 'end of tape'.

Last night I tried a 150mm HP DDS4 tape. (Haven't gone in to work yet) It should easily support the size in native mode, but I'm still worried about the tape unit not compressing the data. When the backup gets larger than 20GBs, I don't want to have to revisit this issue. We have a database that will be getting larger within the next three months.

What do you think?

Thanks again,
Robert

Re: Compression problems with DAT40e & BackupExec

CA769052 — Wed, 27 Mar 2002 18:29:42 GMT

John,

I almost forgot. We are not appending to the backups. Full overwrites.

It looks as if now the backup size is at 19.9GB. It backed up with some errors, but it did complete with the new 150mm tape from HP.

Do you think the performance (POA) will provide me with information if the data is being compressed or not? It appears to be backing up with good speed.

Robert

Re: Compression problems with DAT40e & BackupExec

Patrik Jonsson — Mon, 15 Apr 2002 11:37:24 GMT

Hi there!

I have much of the same problem. I have two DAT-40 drives and none of them passes HP Tape And Library Tools compression tests. The test states that compression is currently DISABLED and fails upon enabling it! My problem arised when the backup failed and i then runned the compression test.

Re: Compression problems with DAT40e & BackupExec

CA756694 — Tue, 30 Apr 2002 13:38:14 GMT

Sorry,

I have been away and I am really busy !

The performance is important as the way I understand it, if your drive is struggling to stream data then it will write 'preambles' on the tape. While these are not large in themselves, they can add up over 20Gb.

However, this does not solve your initial problem of not seeming to even hit your native capacity. Have you both software and hardware compression enabled ?

As to the other chap with the compression test issues with LTT. I will need to see some LTT generated logs. Please post your email and I will contact you.

cheers

John

Re: Compression problems with DAT40e & BackupExec

Andi_2 — Fri, 19 Jul 2002 06:57:45 GMT

Same problem here only with a c1537 DDS3 Drive (on ArcServe 2000 or Backup Exec). It stores max. 11GB to a DDS3 Tape.
Any Idea ?

Re: Compression problems with DAT40e & BackupExec

CA756694 — Fri, 19 Jul 2002 07:21:07 GMT

http://bizforums.itrc.hp.com/cm/QuestionAnswer/1,,0xc30e36e69499d611abdb0090277a778c,00.html

cheers

John