I just finished testing staging and I did find some qotchas with this
configuration. In my test I had 3 areas and I set the default capacity of each
area to be a third of the available disk space. Without setting the default
capacity or
setting it to the size of the disk area caused some other issues so I recommend
using the one third approach.

  1. The high and low water marks go by the available disk space and do not the
     follow the space left in one of the FS devices. Therefore, even if a FS
     device is over the high-water mark, a check file system will not write
     savesets off to tape unless the available disk space is over the high-water
     mark.
  2. Problem 1 lead to FS devices becoming 100% full and legato marking the
     associated volume as (R)ead only. Legato will not set the volume to
     appendable once space becomes available. You must do this manually by
     unmounting and changing the mode on the volume.
  3. When a check file system does run and the disk space is over the high-water
     mark I could not get the low-water mark to work. All 3 area were cleaned up
     completely. If you plan to leave savesets on disk for as long as possible
     this can be an issue. My testing was with small disk areas over short
     periods of time which may have something to do with the results.
  4. If you run out of available disk space during a backup and all 3 FS devices
     are marked read only a check file system will clean the areas up leaving
     the savesets that are currently being backed up. Once you set the volumes
     to appendable the backup will complete BUT if the backup picks the same FS
     device to finish writing a saveset it will OVERWRITE the saveset on disk
     starting from the beginning of file. When you go to write this saveset to
     tape it will give you errors that part of the saveset is lost. This marks
     the saveset as bad and you lose the backup. You must now manually correct
     this situation to get the disk space back. If you run into this problem I
     suggest you add a tape to the staging pool and complete the backup to tape.
     You can later change one of the FS devices to be in a clone pool then use
     nsrclone to write the savesets on the tape back to disk. A stage all
     savesets operation will then put them in their correct home. Another option
     is to add another FS device if you have available disk space somewhere
     else.

It is possible but if you are running on small disk area that periodically run
out of space then you must be very careful.

FYI,
Jon

Joel Fisher wrote:

> Hey All,
>
> I would like to get around the odd limitation of not being able to stage
> savesets to tape while the File System device has an incoming saveset
> stream.  Is there any reason not to have multiple directories setup as
> FS devices under one physical device?
>
> For Example:
>
> /dev/dsk/c3t0d0s2 is mounted on /fsdevices
> 3 directories call:
> /fsdevices/fd00
> /fsdevices/fd01
> /fsdevices/fd02
>
> FS devices setup pointing to the above 3 directories.
>
> Would this allow me to start staging savesets on FS device fd00 and fd01
> even if data is still being written to fd02?
>
> Any known gotchas in this configuration?
>
> Thanks,
>
> Joel
>

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