One possibility is network errors.  Since the majority of the data
flow is in the opposite direction during restore, you may observe
networking issues only during restore.  netstat should provide some
clues here.

System utilization may be an issue.  Generally, backups are done
during off-hours when the disks and network are not doing other
things.  Restores often happen during peak hours.

Writing to disk/filesystems will almost always be slower than
reading.  RAID5 is an obvious culprit.  Any RAID level which involves
mirroring will write at the lowest disk speed, but read at the
highest.  I've got a fileserver at home with mirrored disks where I'll
see timeouts and bus resets only under heavy write load for example.
You may also be dealing with logging/journalling at both a volmue
manager and filesystem level.  If a volume manager has a log region
which is on a slower disk, or worse yet the same disk(s) as the data,
you're going to see a write hit.  Likewise a journalling/logging
filesystem will require additional operations when writing (if you're
doing a full filesystem restore, you may want to consider mounting the
filesystem with logging disabled during the restore, especially if you
would simply restart the full restore in case of a failure).

Use of multiplexing MAY be an issue.  Certainly NBU can read data off
of a non-mpx tape faster since the image will cover less physical
tape.  I'm not sure though that mpx would make restore any slower than
backup, just slower than non-mpx restore assuming that there are no
other bottlenecks.

If you've increased the NUMBER_DATA_BUFFERS to gain performance, you
may need to increase the NUMBER_RESTORE_DATA_BUFFERS (I think that's
it) accordingly.  Given the numbers you've provided, I doubt this will
affect you though.

I'm curious whether a mismatch in the NET_BUFFER_SZ could cause
differences in performance depending on data flow direction.  Again, I
don't think this would affect you, but I'd be interested to know if
you have adjusted them and if so what the values are.


Eric Larrivee writes:
> The restore speed to a Solaris 7 system is considerably slower than the
> speed when backing up that system.  I'm using Netbackup 3.2 and I'm seeing
> and average speed of 400 Kb/sec for restores and about 5 Mb/sec for backups.
> I haven't seen anything in the Netbackup performance tuning guide that would
> help.  How can I speed up the restores and can I expect to see the speed be
> about as fast as the backups?
> 
> thanks,
> Eric
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-- 
Larry Kingery 
       "I command you, as King of the Britons, to stand aside."