I have been looking at the same question: When is an ADSM server full, and
when do I need to order a new one to cope with the extra clients that needs
to be backed up to it?
These are some of the things that affect that choice:-
The capacity of an ADSM Server can be measured in a number of ways. The
actual maximum capacity is a combination of all of these measurements:
· Off-Site Tapes. The main purpose of the ADSM environment is to allow
restores of the IT systems in the case of a disaster recovery invocation.
Therefore, it is important that no more off-site tapes are produced than can
fit into the DLT tape library at the same time.
· On-Site Tape Space. As well as allowing off-site recovery, ADSM also
stores copies of the data it has backed up on on-site tapes. The number of
tapes in use for this purpose must be less than the capacity of the library,
and still allow enough slots to handle the daily off-site tapes that are
produced.
· Disk Cache. When overnight backups take place, the files are first copied
to a disk cache on the ADSM server. This disk cache must be capable of
holding all files modified and backed up each day.
· CPU Power. The system must have enough CPU capacity available to allow the
ADSM processing and database manipulation to take place.
· Database space. The ADSM system must store information about every file
that is backed up. This information is stored in the ADSM database. IBM have
in the past recommended that this database does not grow to more than 20
GBytes.
· Overnight backup window. Client systems are backed up each night. The
systems must be able to backup their modified files within the backup
window, which is approximately 18:00 to 03:00. As more systems are added to
the environment, the intervention between systems causes all processes to
slow down, and can therefore no longer be backed up within the desired time.
· Daily processing. Once the overnight backups from client systems are
complete, the ADSM server must perform its daily processing. This involves
copying data to off-site tapes, backing up the ADSM database, moving
required start up files to a floppy disk, operators moving tapes into and
out of the ADSM server to and from the fire safe, expiring old data,
migrating information to on-site tapes, merging half used tapes together.
This processing must be completed before the next nights backups start.
A new ADSM Server will need to be purchased and implemented before any
individual factor detailed above exceeds the limits or time available.
Cheers,
Chris Jordan
CMG UK Ltd.
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