The interesting quiestion is 'why is it not on by default' and why can you not
set it on on the Default Pool, how silly of them
Maarten
On Thursday 06 May 2004 17:27, you wrote:
> > What exactly is NetWorker doing when auto media verify is enabled?
>
> First the man page definition...
>
> auto media verify (read/write, yes/no, choice)
> If set to yes, NetWorker verifies data written to
> volumes from this pool. Data is verified by re-
> positioning the volume to read a portion of the data
> previously written to the media and comparing the data
> read to the original data written. If the data read
> matches the data written, verification succeeds; other-
> wise it fails. Media is verified whenever a volume
> becomes full while saving and it is necessary to con-
> tinue onto another volume, or when a volume goes idle
> because all save sets being written to the volume are
> complete. [...]
>
> My take is that this is a defense against tape drives that over-buffer.
> Basically it was (or is) possible to run into drives that have large
> buffers for speed, might read 8K of data from the host, but then after
> they acknowledge that the data was received, discover that there's only
> 5K of tape left. Oops.
>
> When the tape is marked full, Networker still has the last block of data
> in memory, so it can go and ask the drive to replay its last block and
> verify that it made the tape. This doesn't take very long and is good
> insurance.
>
> If the verify works okay, the save stream continues on another volume.
> If it fails, the ssid is failed and marked incomplete.
>
> > Does it make sense to have this enabled for a clone pool?
>
> Since the issue is with tapes and drives, I don't see why not.
>
> > I have a pool that I do enable this for because it sounded like it might
> > provide some additional checks, although it probably slows things down,
> > too, I'm sure, and the checks may be cursory at best. I'm thinking I
> > might want to turn it on for the clone as well. Guess it couldn't hurt?
>
> I don't think it slows down anything except when drives stop.
>
>
> --
> Darren Dunham ddunham AT taos DOT
> com
> Senior Technical Consultant TAOS http://www.taos.com/
> Got some Dr Pepper? San Francisco, CA bay area
> < This line left intentionally blank to confuse you. >
>
> --
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