Imported Upstream version 2.4.4p3

[debian/amanda] / docs / WHATS.NEW

This document contains notes on new features in Amanda 2.3 that may
not yet be fully documented elsewhere.

* INDEXING BACKUPS FOR EASIER RESTORE

Read more about this in the file named INDEXING.

* SAMBA SUPPORT

Read more about this in the file named SAMBA.

* GNUTAR SUPPORT

Amanda now supports dumps made via Gnu TAR.  To use this, set your
dumptypes set the program name to "GNUTAR":

        dumptype tar-client {
                ....
                program "GNUTAR"
        }

Since Gnu TAR does not maintain a dumpdates file itself, nor give an
estimate of backup size, those need to be done within Amanda.  Amanda
maintains an /etc/amandates file to track the backup dates analogously to
how dump does it.

NOTE: if your /etc directory is not writable by your dumpuser, you'll have
to create the empty file initially by hand, and make it writable by your
dumpuser ala /etc/dumpdates.

NOTE: Since tar traverses the directory heirarchy and reads files as a
regular user would, it must run as root.  The two new amanda programs
"calcsize" and "runtar" therefore must be installed setuid root.  I've made
them as simple as possible to to avoid potential security holes.


* MULTIPLE BACKUPS IN PARALLEL FROM ONE CLIENT HOST

A new "maxdumps" parameter for the conf file gives the default value for
the amount of parallelism per client:

    maxdumps 2 # default max num. dumps to do in parallel per client

If this default parameter is not specified, the default for the default :-0
is 1.  Then, you can override the parameter per client through the
dumptype, eg:

        dumptype fast-client {
                ....
                maxdumps 4
        }

If the "maxdumps" parameter isn't given in the dumptypes, the default is
used.  The idea is that maxdumps is set roughly proportional to the speed
of the client host.  You probably wont get much benefit from setting it
very high, but all but the slowest hosts should be able to handle a
maxdumps of at least 2.  

Amanda doesn't really have any per-host parameters, just per-disk, so the
per-client-host maxdumps is taken from the last disk listed for that host.

Just to make things more complicated, I've added the ability to specify a
"spindle number" for each filesystem in the disklist file.  For example:

        wiggum /        fast-comp-user  0
        wiggum /usr     fast-comp-user  0
        wiggum /larry   fast-comp-user  1
        wiggum /curly   fast-comp-user  1
        wiggum /moe     fast-comp-user  1
        wiggum /itchy   fast-comp-user  2
        wiggum /scratchy fast-comp-user 3

The spindle number represents the disk number, eg every filesystem on sd0
can get a spindle number of 0, everything on sd1 gets spindle 1, etc (but
there's no enforced requirement that there be a match with the underlying
hardware situation).  Now, even with a high maxdumps, amanda will refrain
from scheduling two disks on the same spindle at the same time, which would
just slow them both down by adding a lot of seeks.

The default spindle if you don't specify one is -1, which is defined to be
a spindle that doesn't interfere with itself.  That is if you don't specify
any spindle numbers, any and all filesystems on the host can be scheduled
concurrently up to the maxdumps.

Just to be clear, there's no relation between spindle numbers and maxdumps:
number the spindles by the disks that you have, even if that's more than
maxdumps.

Also, I'm not sure that putting spindle numbers everywhere is of much
value: their purpose is to prevent multiple big dumps from being run at the
same time on two partitions on the same disk, on the theory that the extra
seeking between the partitions would cause the dumps to run slower than
they would if they ran sequentially.  But, given the client-side
compression and network output that must occur between blocks read from the
disk, there may be enough slack time at the disk to support the seeks and
have a little parallelism left over to do some good.


* MULTIPLE TAPES IN ONE RUN

I've rewritten the taper - it now supports one run spanning multiple tapes
if you have a tape-changer.  The necessary changes in support of this have
also been made to driver and reporter - planner already had support.  There
are a couple other places that should probably be updated, like amcheck.
Dumps are not split across tapes - when taper runs into the end of a tape,
it loads the next tape and tells driver to try sending the dump again.

If you are feeling brave, set "runtapes" to something other than 1.

The new taper also keeps the tape open the entire time it is writing the
files out - no more having amchecks or other accesses/rewinds in the middle
of the run screw you royally if they hit when the tape is closed for
writing a filemark.


* BOTTLENECK DETERMINATION

I've made some experimental changes to Driver to determine what the
bottleneck is at any time.  Since Amanda tries to do many things at once,
it's hard to pinpoint a single bottleneck, but I _think_ I've got it down
well enough to say something useful.  For now it just outputs the current
bottleneck as part of its "driver: state" line in the debug output, but
once I'm comfortable with its conclusions, I'll output it to the log file
and have the reporter generate a nice table.  The current choices are:
        not-idle - if there were dumps to do, they got done
        no-dumpers - there were dumps to do but no dumpers free
        no-hold - there were dumps to do and dumpers free but the dumps
                  couldn't go to the holding disks (no-hold conf flag)
        no-diskspace - no diskspace on holding disks
        no-bandwidth - ran out of bandwidth
        client-constrained - couldn't start any dumps because the clients
                were busy


* 2 GB LIMIT REMOVED

I've fixed the 2-gig limits by representing sizes in Kbytes instead of
bytes everywhere.  This gives us a new 2 TB dump-file size limit (on 32bit
machines), which should last us a couple more years.  This seemed
preferable to me than going to long-long or some other non-portable type
for the size.


* AMADMIN IMPORT/EXPORT

Amadmin now has "import" and "export" commands, to convert the curinfo
database to/from text format, for: moving an amanda server to a different
arch, compressing the database after deleting lots of hosts, or editing one
or all entries in batch form or via a script.


---------------------------------------------------------------------------
Here's the old 2.2.x stuff from this file.  I'm pretty sure most of this
is in the mainline documentation already.
---------------------------------------------------------------------------

This document contains notes on new features in Amanda 2.2 that may
not yet be fully documented elsewhere.

* CLIENT SIDE SETUP HAS CHANGED

The new /etc/services lines are:
    amanda       10080/udp              # bsd security amanda daemon
    kamanda      10081/udp              # krb4 security amanda daemon

The new /etc/inetd.conf lines are:
    amanda  dgram udp wait /usr/local/libexec/amanda/amandad amandad
    kamanda dgram udp wait /usr/local/libexec/amanda/amandad amandad -krb4

(you don't need the vanilla amanda lines if you are using kerberos for
 everything, and vice-versa)


* VERSION SUFFIXES ON EXECUTABLES

The new USE_VERSION_SUFFIXES define in options.h controls whether to
install the Amanda executables with the version number attached to the
name, eg "amdump-2.2.1".  I recommend that you leave this defined, since
the this allows multiple versions to co-exist - particularly important
while amanda 2.2 is under development.  You can always symlink the names
without the version suffix to the version you want to be your "production"
version.


* KERBEROS 

Read the comments in file docs/KERBEROS for how to configure the kerberos
version.  With KRB4_SECURITY defined, there are two new dumptype options:

        krb4-auth       use krb4 auth for this host 
                        (you can mingle krb hosts & bsd .rhosts in one conf)
        kencrypt        encrypt this filesystem over the net using the krb4
                        session key.  About 2x slower.  Good for those root
                        partitions containing your keyfiles.  Don't want to
                        give away the keys to an ethernet sniffer!


* MULTIPLE HOLDING DISKS

You can have more than one holding disk for those really big installations.
Just add extra diskdir and disksize lines to your amanda.conf:

        diskdir "/amanda2/amanda/work"  # where the holding disk is
        disksize 880 MB                 # how much space can we use on it

        diskdir "/dumps/amanda/work"    # a second holding disk!
        disksize 1500 MB

Amanda will load-balance between the two disks as long as there is space.
Amanda now also actually stats files to get a more accurate view of
available and used disk space while running.

* REMOTE SELF-CHECKS

Amcheck will now cause self-checks to run on the client hosts, quickly
detecting which hosts are up and communicating, which have permissions
problems, etc.  This is amazingly fast for what it does: here it checks
more than 130 hosts in less than a minute.  My favorite gee-whiz new
feature!  The new -s and -c options control whether server-only or
client-only checks are done.

* MMAP SUPPORT

System V shared memory primitives are no longer required on the server
side, if your system has a version of mmap() that will allocate
anonymous memory.  BSD 4.4 systems (and OSF/1) have an explicitly
anonymous mmap() type, but others (like SunOS) support the trick of
mmap'ing /dev/zero for the same effect.  Amanda should work with both
varieties.

Defined HAVE_SYSVSHM or HAVE_MMAP (or both) in config.h.  If you have
both, SYSVSHM is selected (simply because this code in Amanda is more
mature, not because the sysv stuff is better).


* GZIP SUPPORT

This was most requested feature #1; I've finally slipped it in.  Define
HAVE_GZIP in options.h.  See options.h-vanilla for details.  There are two
new amanda.conf dumptype options "compress-fast" and "compress-best".  The
default is "compress-fast".  With gzip, compress-fast seems to always do
better than the old lzw compress (in particular it will never expand the
file), and runs faster too.  Gzip's compress-best does very good
compression, but is about twice as slow as the old lzw compress, so you
don't want to use it for filesystems that take a long time to full-dump
anyway.


* MOUNT POINT NAMES IN DISKLIST

Most requested feature #2: You can specify mount names in the disklist
instead of dev names.  The rule is, if the filesystem name starts with a
slash, it is a mount point name, if it doesn't, it is a dev name, and has
DEVDIR prepended.  For example:

        obelix  sd0a            # dev-name: /dev/sd0a
        obelix  /obelix         # mount name: /obelix, aka /dev/sd0g


* INITIAL TAPE CHANGER SUPPORT INCLUDED

A new amanda.conf parameter, tpchanger, controls whether Amanda
communicates with a tape changer program to load tapes rather than
just opening the tapedev itself.  The tpchanger parameter is a string
which specifies the name of a program that follows the API specified
in docs/TAPE.CHANGERS.  Read that doc for more information.

* GENERIC TAPE CHANGER WRAPPER SCRIPT

An initial tape-changer glue script, chg-generic.sh, implements the
Amanda changer API using an array of tape devices to simulate a tape
changer, with the device names specified via a conf file.  This script
can be quickly customized by inserting calls tape-changer-specific
programs at appropriate places, making support for new changers
painless.  If you know what command to execute to get your changer to
put a particular tape in the drive, you can get Amanda to support your
changer.

The generic script works as-is for sites that want to cascade between
two or more tape drives hooked directly up to the tape server host.
It also should work as-is with tape-changer drivers that use separate
device names to specify the slot to be loaded, wheres simply opening
the slot device causes the tape from that slot to be loaded.

chg-generic has its own small conf file.  See example/chg-generic.conf
for a documented sample.

* NEW "amtape" COMMAND

The amtape is the user front-end to the amanda tape changer support
facilities.  The operators can use amtape to load tapes for restores,
position the changer, see what amanda tapes are loaded in the tape
rack, and see which tape would be picked by taper for the next amdump
run.

No man page yet, but running amtape with no arguments gives a detailed
usage statement.  See docs/TAPE.CHANGERS for more info.

* CHANGER SUPPORT ADDED TO "amlabel" COMMAND

The amlabel command now takes an optional slot argument for labeling
particular tapes in the tape rack.  See docs/TAPE.CHANGERS for more
info.


* TAPE CHANGER SUPPORT IMPROVED

The specs in docs/TAPE.CHANGERS has been updated, and the code changed to
match.  The major difference is that Amanda no longer assumes slots in the
tape rack are numbered from 0 to N-1.  They can be numbered or labeled in
any manner that suits your tape-changer, amanda doesn't care what the
actual slot names are.  Also added "first" and "last" slot specifiers, and
an -eject command.

The chg-generic.sh tape changer script now has new "firstslot", "lastslot",
and "needeject" parameters for the chg-generic.conf file.  It now keeps
track of whether the current slot is loaded into the drive, so that it can
issue an explicit eject command for those tape changers that need one.  See
example/chg-generic.conf for more info.


* A FEW WORDS ABOUT MULTI-TAPE RUNS

I'm still holding back on support for multiple tapes in one run.  I'm
not yet completely happy with how Amanda should handle splitting dumps
across tapes (eg when end-of-tape is encountered in the middle of a long
dump).  For example, this creates issues for amrestore, which currently
doesn't know about configurations or tape changers --- on purpose, so
that you can do restores on any machine with a tape drive, not just the
server, and so that you can recover with no online databases present.

However, because the current snapshot DOES support tape changers, and
multiple runs in one day, some of the benefit of multi-tape runs can be
had by simply running amanda several times in a row.  Eg, to fill three
tapes per night, you can put
        amdump <conf>; amdump <conf>; amdump <conf>
in you crontab.  On the down side, this will generate three reports
instead of one, will do more incremental dumps than necessary, and will
run slower.  Not very satisfying, but if you *need* to fill more than
one tape per day NOW, it should work.


* BIG PLANNER CHANGES

The support for writing to multiple tapes in one run is almost finished
now.  See docs/MULTITAPE for an outline of the design.  The planner support
for this is included in this snapshot, but the taper part is not.

There is a new amanda.conf variable "runtapes" which specifies the number
of tapes to use on each amdump run.  For now this should stay at 1, the
default.  Also, the old "mincycle" and "maxcycle" amanda.conf variables are
deprecated, but still work for now.  "maxcycle" was never used, and
"mincycle" is now called "dumpcycle".

There are two visible differences in the new planner: First, Planner now
thinks in real-time, rather than by the number of tapes as before.  That
is, a filesystem is due for a full backup once every <dumpcycle> days,
regardless of how many times amanda is run in that interval.  As a
consequence, you need to make sure the dumpcycle variable marks real time
instead of the number of days.  For example, previously "mincycle 10"
worked for a two week cycle if you ran amdump only on weekdays (for 10 runs
in a cycle).  Now a two week cycle must be specified as "dumpcycle 14" or
"dumpcycle 2 weeks".  The "2 weeks" specifier works with both the old and
new versions of planner, because previously "weeks" multiplied by 5, and
now it multiplies by 7.

Second, planner now warns about impending overwrites of full backups.  If a
filesystem's last full backup is on a tape that is due to be overwritten in
the next 5 runs, planner will give you a heads-up about it, so that you can
restore the filesystem somewhere, or switch that tape out of rotation
(substitute a new tape with the same label).  This situation often occurs
after a hardware failure brings a machine or disk down for some days. 

* LEVEL-0 DUMPS ALLOWED WITH NO TAPE

If there is no tape present (or the tape drive fails during dumping),
Amanda switches to degraded mode.  In degraded mode, level-0 dumps
are not allowed.  This can be a pain for unattended sites over the
weekend (especially when there is a large holding disk that can hold
any necessary dumps).  Amanda now supports a new configuration file
directive, "reserve".  This tells Amanda to reserve that percentage
of total holding disk space for degraded mode dumps.  Example: your
total holding disk space adds up to 8.4GB.  If you specify a reserve
of 50, 4.2GB (50%) of the holding disk space will be allowed to be
used for regular dumps, but if that limit is hit, Amanda will switch
to degraded dumps.  For backward compatibility, if no 'reserve' keyword
is present, 100 will be assumed (e.g. never do full dumps if degraded
mode is in effect).  NOTE: this percentage applies from run to run, so,
as in the previous example, when Amanda runs the next day, if there is
3.8GB left on the holding disk, 1.9GB will be reserved for degraded
mode dumps (e.g. the percentage keeps sliding).