Using AMANDA
This is an excerpt from the
book Unix Backup & Recovery. This
page is only part of the AMANDA chapter that is available here
for free.
Decide Which Tape Devices to Use
Unix operating systems typically
incorporate device characteristics into the file name used to access a
tape device. The two to be concerned with are “rewind” and “compression.”
AMANDA must be configured with the non-rewinding tape device, so called
because when the device is opened and closed it stays at the same position
and does not automatically rewind. This is typically a name with an n in
it, such as /dev/rmt/0n. On AIX, it is a name with a .1 or .5 suffix.
Put the AMANDA user in the
group that currently owns the tape device, either as the primary group
or as a secondary, or pick a new group for AMANDA and change the group
ownership of the device. AMANDA needs both read and write access. Turn
off all “world” access.
Decide Whether to Use Compression
Dump images may optionally be
compressed on the client, the tape server, or the tape device hardware.
Software compression allows AMANDA to track usage and make better estimates
of image sizes, but hardware compression is more efficient of CPU resources.
Turn off hardware compression when using software compression on the client
or server. See the operating system documentation for how hardware compression
is controlled; on many systems it is done via the device file name just
like the non-rewinding flag. AIX uses the chdev command.
Decide Where the Holding Space Will Be
If at all possible, allocate
some holding disk space for AMANDA on the tape server. Holding disk space
can significantly reduce backup time by allowing several dumps to be done
at once while the tape is being written. Also, for streaming tape devices,
AMANDA keeps the device going at speed, and that may increase capacity.
AMANDA may be configured to limit disk use to a specific value so it can
share with other applications, but a better approach is to allocate one
or more inexpensive disks entirely to AMANDA.
Ideally, there should be
enough holding disk space for the two largest backup images simultaneously,
so one image can be coming into the holding disk while the other is being
written to tape. If that is not practical, any amount that holds at least
a few of the smaller images helps. The AMANDA report for each run shows
the size of the dump image after software compression (if enabled). That,
in addition to the amplot and amstatus tools, may be used to tune the space
allocated.
Copyright (c) 2000, O'Reilly
and Associates. All Rights Reserved.
|
