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WHAT IS AMANDA?
---------------
This is an alpha-test release of Amanda, the Advanced Maryland Automatic
Network Disk Archiver. Amanda is a backup system designed to archive many
computers on a network to a single large-capacity tape drive. This release
is currently in daily use at the University of Maryland at College Park
Computer Science Department, backing up all the disks on all the
workstations in the department: currently over 70 gigabytes of data across
more than 400 filesystems on more than 146 workstations and servers, using
a single 5 Gigabyte Exabyte EXB-8500. Here are some features of Amanda:
* written in C, freely distributable.
* built on top of standard backup software: BSD Unix dump/restore, and
later GNU Tar and others.
* will back up multiple machines in parallel to a holding disk, blasting
finished dumps one by one to tape as fast as we can write files to
tape. For example, a ~2 Gb 8mm tape on a ~240K/s interface to a host
with a large holding disk can be filled by Amanda in under 4 hours.
* does simple tape management: will not overwrite the wrong tape.
* supports tape changers via a generic interface. Easily customizable to
any type of tape carousel, robot, or stacker that can be controlled via
the unix command line.
* supports Kerberos 4 security, including encrypted dumps. The Kerberos
support is available as a separate add-on package, see the file
KERBEROS.HOW-TO-GET on the ftp site, and the file docs/KERBEROS in this
package, for more details.
* for a restore, tells you what tapes you need, and finds the proper
backup image on the tape for you.
* recovers gracefully from errors, including down or hung machines.
* reports results, including all errors in detail, in email to operators.
* will dynamically adjust backup schedule to keep within constraints: no
more juggling by hand when adding disks and computers to network.
* includes a pre-run checker program, that conducts sanity checks on both
the tape server host and all the client hosts (in parallel), and will
send an e-mail report of any problems that could cause the backups to
fail.
* can compress dumps before sending over net, with either compress or gzip.
* can optionally syncronize with external backups, for those large
timesharing computers where you want to do fu--------------------------------------------
Amanda requires a host that is mostly idle at night, with a large capacity
tape drive (e.g. an EXABYTE or DAT tape). This becomes the "tape server
host". All the computers you are going to dump are the "backup client
hosts". The server host can also be a client host.
Amanda works best with one or more large "holding disk" partition on the
server host available to it for buffering dumps before writing to tape.
The holding disk allows Amanda to run backups in parallel to the disk, only
writing them to tape when the backup is finished. Note that the holding
disk is not required: without it Amanda will run backups sequentially to
the tape drive. Running it this way kills the great performance, but still
allows you to take advantage of Amanda's other features.
As a rule of thumb, for best performance the holding disk should be larger
than the dump output from your largest disk partitions. For example, if
you are backing up some full gigabyte disks that compress down to 500 MB,
then you'll want 500 MB on your holding disk. On the other hand, if those
gigabyte drives are partitioned into 500 MB filesystems, they'll probably
compress down to 250 MB and you'll only need that much on your holding
disk. Amanda will perform better with larger holding disks. We use 800 MB
for our holding disk.
Actually, Amanda will still work if you have full dumps that are larger
than the holding disk: Amanda will send those dumps directly to tape one at
a time. If you have many such dumps you will be limited by the dump speed
of those machines.
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