Hi Sri,

        You cannot assume that Tapes, Optical, or even good old magnetic
hard drives are right or wrong for every situation.

        You need to evaluate your environment. For example, Tape is
cheapest, because you can pack a ton of data on each tape. Tape also has
the advantage of going off site, or being restored to another site. The
down side of tape is that is relatively slow when you compare it to a
random access device such as disk. Magnetic hard disks are much more
expensive when you look at the cost per megabyte (or are they measuring
that in GB's now). Disks are fast, but they take up space and cannot
easily be taken off site. Optical can be looked at as kind of a hybrid.
They  are expensive, but they enjoy the advantages of random access and
portability offsite for storage. Optical can also be stored for a long
time, which means that they are often the choice for archive.

        You are lucky to have 270GB of optical. Most people who have
optical, use it for Archive, and do not have the luxury of using it as a
primary storage pool. At our site we move a lot of our data to disk to
take advantage of the speed of the disks, and going to disk also gives
the ability to do parallel backups. We have our system set up so that
any files over 200MB are moved directly to tape, because these will
eventually go to tape anyway and we don't save a lot going to disk
first. When our backups are done the data that now resides on the local
disk and tape is copied to a second set of tapes to be sent off site.
Once that is complete, the data on the disks is then copied to the local
tapes. Now we have a copy of the data on 2 sets of tapes. One on site,
and one off.

        If we had optical and had no serious Archive goals it would be
great. We would probably have a similar setup to the one we currently
do, but we would only allow data to flow to the optical depending on the
critical-ness of the data. If the data needs to be restored quickly keep
it on the optical. Make a duplication of the local data to a tape for
off-site storage. If the data is of a lower priority, keep a local copy
on tape, and create an off site copy for redundancy.


Hope this helps.

Ed.

> -----Original Message-----
> From: Gogineni, Sri [SMTP:SGogineni AT CAISO DOT COM]
> Sent: Thursday, July 30, 1998 4:56 PM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Storage pool space
>
> Hi,
>    We would soon be reaching a stage where we would need more storage
> spool space. Presently we are trying to reclaim space from the 270Gb
> opticalpool. I understand that offsite ( tapes / optical disks) are
> good
> only for copypools and not for primary storage pools.
>
> My question is whether It is possible to use  additional (tapes/
> opticaldisks) inside the primary storage pool and enhance its
> capacity.
> If not Is it possible to enhance the storage capacity by adding
> another
> opticallibrary( Even if we have to split it into multiple storage
> pools.) ?
>
> Any guidance is appreciated.
> Thanks in advance
> Gogineni