Topic: Fixed block size tape drives

[judgej]

This is something I had to do years ago for an old e-smith 5.1.2 system, and since I have only just upgraded to 6.0.1, had to do it again, so thought I would docement the procedure in case it is of use to others.

Basically, some tape drives will only write to a fixed block size. One example is the ST9000 12/24 DDS3 drive, used by Compaq. I suspect Compaq have used their own BIOS, but the upshot is that the drive will only write correctly in blocks of 64k.

I fixed this by an addition to the SME config. In file /home/e-smith/configuration you will find the following line:

flexbackup=backupservice|erase_rewind_only|true

Edit that line to set the write block size, in this case to 64k:

flexbackup=backupservice|erase_rewind_only|true|TapeBlocksize|64

Then expand the template:

/sbin/e-smith/expand-template /etc/flexbackup.conf

That's it. Now the Compaq 12/24 SCSI DDS3 drive will work with SME6.0.1.

I hope that is of use for someone, because it took me long enough the first time round to fix the problem.

As always: make a backup if you are not fully confident about the changes you are making.

I would also advise anyone who backs up to tape, to test their backups to ensure they work. You can use flexbackup from the command line to list the content of the tape to a file, or to extract a tape to an i-bay for inspection. The one time you don't want to find the tape backup is not set up correctly is when you need to do a system restore. In the case of the ST9000, e-smith 5.1.2 gave write errors when backing up, alerting me to a problem. However, SME 6 gave me no such errors, but it did produce a tape that could not be read - it just did so without a whimper.

-- Jason

[ldkeen]

Jason,
A better way to do it is
#mcedit /etc/e-smith/templates/etc/flexbackup/10Blocksize
Make the change there then do:
#/sbin/e-smith/expand-template /etc/flexbackup
A word of warning - after extensive testing I have found that the restore process trashes the permissions for all users and ibays (as well as samba profiles). I don't know whether this has to do with modifying the blocksize yet, I still have to do more testing. Also when you go to restore to a new system you HAVE to change the blocksize in the configuration of the new box to match the blocksize of the tape that you will be restoring from otherwise it will fail. Have you done a restore from tape of a blocksize modified box yet? I'm trying to work out whether it's the actual backup or the restore process that trashes the permissions.

[judgej]

Jason,
A better way to do it is
#mcedit /etc/e-smith/templates/etc/flexbackup/10Blocksize
Make the change there then do:
#/sbin/e-smith/expand-template /etc/flexbackup
A word of warning - after extensive testing I have found that the restore process trashes the permissions for all users and ibays (as well as samba profiles). I don't know whether this has to do with modifying the blocksize yet, I still have to do more testing. Also when you go to restore to a new system you HAVE to change the blocksize in the configuration of the new box to match the blocksize of the tape that you will be restoring from otherwise it will fail. Have you done a restore from tape of a blocksize modified box yet? I'm trying to work out whether it's the actual backup or the restore process that trashes the permissions.

Yes, I have tried restoring to an i-bay, and it works fine - the files are recovered at least, though I haven't checked permissions etc. Before a restore, then the blocksize would need to be changed on the box being restored - that seems reasonable.

This blocksize restriction is just due to some wierd BIOS change that Compaq have made to the DAT drives. Apart from that, they are standard Sony or Seagate mechanisms, and really shouldn't need this kind of hack.

On changing that template: no, I would advise not to. At the very least, create a custom template with the change in. However, if you do create a custom template, then you need to ensure the custom template tracks any changes to the core template that may be made during updates. To my mind, setting the configuration item and leaving the templates well alone is the best approach. The core templates are designed to read that configuration item.

-- Jason

[CharlieBrady]

Jason,
A better way to do it is
#mcedit /etc/e-smith/templates/etc/flexbackup/10Blocksize
Make the change there then do:
#/sbin/e-smith/expand-template /etc/flexbackup

Why do you say that is a better way of doing it? You should *never* edit template files - create a custom template file if you wish to make a change. But in this case, there is already a database property which allows blocksize to be configured (as in the parent post), and that is the better way to make this change.

A word of warning - after extensive testing I have found that the restore process trashes the permissions for all users and ibays (as well as samba profiles).

Have you reported the problem, and the results of your investigations to the Bug Tracker at this website?