On Thu, Jan 23, 2003 at 01:53:07AM -0500, Scott Mcdermott wrote:
> After searching around in the FAQ-O-MATIC, current projects page, and in
> the mailing list archives, I believe what I understand is that:
> 
>    - the largest filesystem backed up must be smaller than the size of
>      the tapes used (possibly after compression is considered)

False.  It can not backup "disklist entries (DLEs)" larger than a tape.
If gnutar is used as the backup program for a DLE it need not be the
entire file system, but a directory tree.  The DLE then specifies the
starting directory of the tree.
> 
>    - amanda can't do hardware compression without breaking easily

False.  Many use hardware compression very happily.  The issue is that
DLE's vary greatly in their compressibility.  Some of mine compress to
20% of their original size, others to 95%.  For some tasks, amanda would
like to know how much tape a backup is going to use.  If she doesn't
compress it, she doesn't know for sure.  But she certainly does not break.
> 
>    - amanda doesn't do parallel backups under any circumstances

Not sure what you are looking for in parallelism.  Certainly amanda can
simultaneously backup multiple DLE's from a single or multiple clients.
Amanda can't run multiple configurations (say a daily and a monthly config)
at the same time.
> 
> do I understand these points correctly? I have several issues this will
> create for me and no idea how to solve them:
> 
>    - I have some filesystems that are LARGE and have no hope of fitting
>      on a single tape, and no hope of fitting in a staging/holding area
>      on a disk.  These are large logical volumes that span across
>      multiple RAID arrays.  Amanda simply can't handle these because it
>      can't span tapes, correct?

See above
> 
>    - I have a nice fast compression ASIC in my tape drives which can
>      probably compress at the drive's write speed, while my backup host
>      is slow and intended mainly for IO.  Do I have it right that Amanda
>      can't just write until EOT (allowing the drive to compress), rewind
>      to last EOF, and move on to the next tape? Instead I have to use
>      CPU in my backup server to do compression?

See above
> 
>    - my library has 4 drives in it, which can all write at once.  Do I
>      need to go out and buy 3 more backup hosts, split up my changer's
>      SCSI bus and partition the library into 4 virtual libraries in
>      order to actually do concurrent backups? Maybe I can run separate
>      amdump instances that don't know anything about each other? ugh :)

I'm not familiar with using multiple drives.  However amanda did introduce
a RAIT capability last year.  It is my understanding that this can be used
for mirroring, striping, ???  I'm sure others will answer.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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