You'll quickly learn that the default 8meg storage pool is extremely
     inadequate for extend testing. You'll also find that the 8mm tape
     device is extremely slow.
     I would recommend very large disk storage pools (the 75% high water
     mark is ok if the pool is large enough).
     Your goal is to size the DISK POOL so that the incoming backup data
     can be written to the disk pool without having to wait for the TAPE
     process to drain it off.
     Even for testing purposes I would make your disk pool as large as
     possible.
     I am using 1.5gig for my testing on a Sun platform right now, with the
     secondary pool being a 8mm tape. The 75% high water mark is Ok. I can
     overwhelm the process if I allow enough backups to run at the same
     time, but with this config I am able to run multiple full backups
     without having to wait for the migration process to drain off the disk
     pool. We are planning on a 16gig primary disk pool when we move into
     production, with several higher speed DLT transports as the secondary.

     Mike Lewandowski
     First Chicago NDB


______________________________ Reply Separator _________________________________
Subject: Pointers for optimizing backup performance
Author:  ADSM-L AT VM.MARIST DOT EDU at INTERNET
Date:    4/24/96 5:13 PM


We're still testing this stuff out and I'm certainly not a point of
performance tuning.  However, I'm confused on what type of ideal settings
to use.  I just have the basic staging pool on magnetic disk with the tape
pool next in line.  The magneteic storage area is only 8Mb.  What are the
ideal migration settings for that storage pool to get a smooth flow of
data going to tape (8mm for right now)?  Larger pool?  Very low migration
threshholds?  Not sure what is best here.

___________________________________________________________
Joe Morris - morris AT unc DOT edu - http://sunsite.unc.edu/morris
OIT/Computing Systems, Development
University of North Carolina at Chapel Hill