Really strange problem with slow throughput

[Laurie_Rose]

We run Backup Exec 8.5 on a Windows 2000 server. It backs up both local files, and those on a 100Mbps-LAN-attached Windows 2003 server, to a Dell PowerVault 120T autoloader containing a Dell DLT7000 (Quantum DLT) drive. BE and the drive h/w are all at the latest (well, least ancient) driver and firmware levels.
The Windows 2003 server is running the Remote Agent.

Now it gets weird ...

- All backup sets of local folders run fast; 250-300MB/min
- Backups of some folders on the remote server also backup fast; 250MB/min
- Backups of other folders on the remote server (some of which are in the same partition as "quick" ones) go really slowly; 25-35MB/min).
- Overall, the entire backup job of around 40GB takes up to 10 hours

EXCEPT that on alternate Tuesdays and Wednesdays, when the backup tapes happen to be Maxell brand, every set runs quickly and the whole job takes around three hours. Other tapes in the backup sets are either Fuji or Sony DLT IV.

So - I can eliminate block/buffer size/ SCSI parameters, fragmented drives,dirty heads, network and configuration errors because there's no problem with Maxell tapes or some network folders with other tapes.

Even odder, the Maxell tapes are the oldest ones we use. The Sonys and Fujis are much newer (some brand new) and they show a lot more soft write errors than the Maxells. But they have no problem backing up local files.

We must be getting some subtle timing problem but I've no idea how to crack this. The soft write errors ought to be a clue Do we just have a fussy drive?

[Ken_Putnam]

Do we just have a fussy drive?

It's possible.

I know tapes are expensive, but have you considered getting one new Maxell tape to see it that works?

Is it the same job that runs every day of the week, or do you have separate Daily Jobs? If separate jobs, try recreating one to see it that makes a difference

[Laurie_Rose]

The only difference between daily jobs is the autoloader slot (Monday = slot 1, Tuesday = slot 2 etc) . They all use the "Monday" file selection list. I have tried putting a Maxell tape in slot 4 (Thursday) and then the job ran quickly.

Do Maxell (and indeed Sony, Fuji et al) actually make their own DLT tapes in separate factories, or do they brand generics from a single source?

I just wondered if, since our drive is pretty old and old tapes work better than new ones, whether someting has changed in the tape formulation and we'll have the same problem with any new tapes, including Maxell. Only one way to find out I suppose ...

[Laurie_Rose]

I can answer part of my own followup quetion. According to Wikipedia:

"Current manufacturers of cartridges for the DLT/SDLT market are Fujifilm, Hitachi/Maxell and Imation. VStape is made by Sony. All other companies/brands (even Quantum) are contractors and/or resellers of these companies."

[Laurie_Rose]

We had the drive serviced and the engineer confirmed our findings (fine with Maxell, not good with Fuji). We bought some new Maxell tapes and it's fine.

Look out for 12 or so hardly-used Fuji DLT IV tapes on eBay real soon now!