There are several keys to speed in restoring a large number files with TSM;
they are:
  1.. If using WindowsNT/2000 or AIX, be sure to use DIRMC, storing primary
pool on disk, migrate to FILE on disk, then copy-pool both (this avoids tape
mounts for the directories not stored in TSM db due to ACL's);
  I've seen *two* centralized ways to implement DIRMC -- (1) using
client-option-set, or (2) establish the DIRMC management class as the one
with the longest retention (in each affected policy domain);
  2.. Restore the directories first, using -DIRSONLY (this minimizes NTFS
db-insert thrashing);
  3.. Consider multiple, parallel restores of high-level directories --
despite potential contention for tapes in common, you want to keep the data
flowing on at least one session to maximize restore speed;
  4.. Consider using CLASSIC restore, rather than no-query restore -- this
will minimize tape mounts, as classic restore analyzes which files to
request and has the server sort the tapes needed -- though tape mounts may
not be an issue with your high-performance configuration;
  5.. If you must use RAID-5, realize that you will spend TWO write cycles
for every write;  if using EMC RAID-S (or ESS), you may want to increase
write-cache to as large as allowed (or turn it off, altogether).  Using 9 or
15 physical disks will help. A client of mine just had a server disk failure
last weekend;  it had local disk configured with RAID-5 (hardware RAID
controller attached to Dell-Win2000 server) -- after addressing items 1 to
3, above, we were able to saturate the 100Mbps network, achieving 10-15
GB/Hr for the entire restore -- only delays incurred were attributable to
tape mounts... this customer had an over-committed silo, so tapes not in
silo had to be checked-in on demand.  316 GB restored in approx. 30 hours.
Their data was stored under 10 high-level directories, so we ran two restore
sessions in parallel -- only had two tape drives -- and disabled other
client schedules during this exercise.

For your situation, 250 GB and millions of files, and assuming DIRMC (item
#1, above), you should be able to see 5 - 10 GB/Hr -- 50 hours at 5 GB/Hr,
25 hours at 10 GB/Hr.  So you are looking at two or three days, typically.

Large numbers of small files is the "Achilles Heal" of any file-based
backup/restore operation -- restore is the slowest (since you are fighting
with the file system of the client OS) because of the way file systems
traverse directories and reorganize branches "on the fly", it's important to
minimize the "re-org" processing (in NTFS, by populating the branches with
leaves AFTER first creating all the branches). We did some benchmarks and
compared notes with IBM;  on another client, we developed the basic
expectation that 2-7 GB/Hr was the "standard" for comparison purposes -- you
can exceed that number by observing the first 3 recommended configuration
items, above.

How to mitigate this:  (a) use image backup (now available for Unix, soon to
be available on Win2000) in concert with file-level progressive incremental;
and (b) limit your file server file systems to either 100 GB or "X" million
files, then start a separate file system or server upon reaching that
threshold... You need to test for your environment to determine what is the
acceptable standard to implement.

Hope this helps.

Don France

Technical Architect - Tivoli Certified Consultant



Professional Association of Contract Employees (P.A.C.E.)
San Jose, CA