hp-ux and sony ait-3 drive warning to users

[AMSA Unix Admin]

We bought a couple of sony ait-3 drives for our backup system. Our server is hp-ux 11.0. Unfortunately, by default HP-UX prevents AIT-3 drives from supporting h/w compression (DC) and sends a signal to disable. So the 100-260GB capacity drives become 100GB max. We observed this by using SCSI trace while running 'dd' - HP-UX clearly turns OFF DC. So we used a utility that will change the drive ID string to Sony SDX-300C, this corresponds to an AIT-1 drive. The drive compression then worked properly. good. This was several months ago. Today I needed to use fbackup to write to the drives, however I got an error message that it is not a valid device. So I change the SCSI Inq string to 'HP C1537A' (a DDS3 I think) and the fbackup works. I am not sure but it certainly seems that HP is intentionaly making it so that Sony AIT drives will not function properly on the HP-UX servers. Is this a way to leverage the LTO market? I don't know but it seems very improper. Unless HP resolves this apparent impropreity, our next server will be a SUN. I am very disgusted by how this appears - I wonder if HP can offer an worthy explaination???

[John Payne_2]

If you are up to date on patches for your system (And even if you are not...) I would open a call to HP software support and ask them. Chances are is that it is supported, but you have to either install a patch or do something a little different.

We do not use AIT here, but that is what I bet is happnening...

Hope it helps
John

[AMSA Unix Admin]

Thanks John,

We are up to date patch-wise, I put the latest bundle on a few weeks ago. I do plan on opening a ticket because it certainly is not the performance we expected .

Regards,

Chuck Davis

[Vincent Farrugia]

Hello,

Unfortunately that is what can happen if you use unsupported hardware... HP has their own tapes drives; Ultrium tape drives.

HTH,
Vince

[Doug Rauenzahn]

Sony AIT drives are not supported on HP-UX. The stape driver uses the inquiry data returned by the device to identify the drive. If the driver does not recognize the inquiry data (ie, an AIT drive), then it marks the drive as unknown or drive type MT_ISUNKNOWN as defined in sys/mtio.h. Before fbackup will access a drive, it asks the driver for the device type and verifies that it is a known type (ie, MT_ISDLT, MT_ISDDS, ect). If the device type is unknown, then fbackup will not backup to the device. Fbackup did work when you changed the device to be a DDS drive because the driver now recognized the drive and fbackup accepts DDS type drives.

The reason the drives compression is being turned off is because the default behavior the driver uses for unknown drives is to turn compression off with the BEST device files. If you want to use your drive at full capacity outside of fbackup, I'd suggest you create your own device file using mksf and set the density and compression on.

I believe the drive will select the proper density for the media like DDS, so you could use the following mskf command with the old AIT-1 density.

mksf -d stape -I -v -b 48 -c 3 -u -n

This will create a device file with density 0x30, compression on, no-rewind on close, and Berkeley style close. Check out the man page for mksf (stape sectin) for more details. That should get you using compression.

Now, for fbackup. You can try setting the inquiry data to a DDS drive as you did before, and using the device file created above.

Please remember that these devices are not officially supported as they have not gone through the normal HPUX tape drive qualification process, but you should be able to "make it work".

[Terry Davlin]

I've been pretty disgusted with the performance of the AIT-3, too; but it's working properly now. I created the device as suggested by Doug Rauenzahn, and was able to get 91 gb instead of 48 gb. Finally, on my rp5470 running 11.11, the fix was to add stape/kernel patch PHKL_28217. I then created another device, e.g.:

mksf -d stape -I 0 -v -b 48 -c 3 -n /dev/rmt/c6t0d0D48C3nb

with which vxdump put 5 file sytems, totaling 245gb, on a tape. I was able to vxrestore a sampling of files from each dump without any problem.

Thanks to Forum participants and to Dawn and George at tech support, we will keep the rp5470. Failure to get AIT-3 working surely would have been a deal-breaker for future HP purchases.

Hope this works for everyone else,

Judith

Judith

[Hans_23]

How did you change the inquiry string?