No Hardware Compression with HP Surestore dat40 (C5683A)

[Steve Benson_2]

The drive was not in use prior to last week.

It was in a system but a tape library DLT was used on another system for server backups.

When migrating to new servers I thought (silly me :)) while I was re-configuring the old servers I'd go ahead and configure this unused drive for potential use.

So, it's not a critical exercise but something of a frustration that it doesn't seem to be working correctly.

I cleaned the drive with a new cleaning tape. The tapes I'm useing are not new but have been used very little and are HP gold dds4 tapes.

I've checked the tapes with the media validation tests and they pass.

I've used the same tapes for the L&TT compression ratio test and they work fine, compression ratio reported by L&TT is 2.23:1.

All the L&TT tests (I've run each one several times) pass.

S/W compression has never been used, always hardware only or none (none used in the test of the 2-3 off test enable/no host control).

This is especially frustrating since I've been configuring backup systems with Backup Exec and Arcserve (and one Leggato Network Archivest) for many years, since '91 and have never encountered this problem before.

Admittedly this is the first time I've used an HP DAT 4.

I thought I'd create a directory and fill it with text only files in excess of 20GB and see what happens when I backup that dir.

I think that would eliminate the possiblitity of this all being caused by compression ratios on diff file types.

Any thoughts?

[Steve Benson_2]

Good news, I think.

I created a couple of simple ascii text files of 200 and 300 MB and then made duplicate copies in a directory until I had 29.5GB of data.

To my chagrin when I ran a backup it took the entire 29.5 GB on one tape.

Seems the compression algorythm on this drive is unable to compress 90+% of the files on my server.

Most of the files on this server are binary in nature, very few text files.

Of course I realize the compression ratio varies with the file types.

This was just cooincidentally getting a 1:1 or less ratio on the first tape which I mistook for a limitation due to the tape's native capacity.

When I've used other drives, mostly Exabytes, the compression seemed to work on most files and gave close to the specification compression ratio.

Well, live and learn I guess.

I certainly would like to thank everyone for their input and time.

Sorry it seems to have been such a silly thing.

........ Steve