Amanda-Users

Re: Holding Space Size and autoflush

2005-04-26 12:11:18
Subject: Re: Holding Space Size and autoflush
From: Jon LaBadie <jon AT jgcomp DOT com>
To: amanda-users AT amanda DOT org
Date: Tue, 26 Apr 2005 11:51:06 -0400
On Tue, Apr 26, 2005 at 09:49:12AM -0400, Kuas wrote:
> I didn't have autoflush turn on before (in amanda.conf), I thought
> amanda will flush the content of the holding disk to the tape(=slot,
> since I am using file-driver). Is this right? Then I found a problem
> with amdump, in the log said that it does not have holding disk anymore.
> How big is the holding disk supposed to be? Equal to the size of each
> tape? I left it default: use 290 Mb and chunksize 1GB, while my tape
> size is 4GB for now.
>

Think about traditional tapes, not your vtapes.  Only one thing
can be writing to the tape drive at a time.  But ...

I may have 50 clients, each with multiple DLE's.  Do I really
want to dump 1 DLE at a time through hundreds of DLE's?  Probably
not, so I want to be dumping 2, 5, 10, 25 DLE's all at the same
time, but only one thing can be writing to the tape at a time.
The holding disk is used to collect those DLE dumps while they
are in progress and the completed dump until it can be transfered
to tape (the one thing writing to tape remember).

If you use no holding disk, or the available space in the holding
disk is too small, then that DLE is written directly to tape, i.e.
the one thing writing to the tape is a dump in progress, not the
transfer of a completed dump.

Your holding disk is probably doing you no good at all.  Unless
you have several DLE's substantially less than 292MB (maybe incre-
mentals).  And the pair, 292MB with allowed "chunks" of 1GB is
kind of silly.  Tough to fit a 1"G"B chunk on a 292"M"B disk.
Also, if you used defaults, the "reserve" is 100 meaning 100%
of the holding disk can not be used for level 0 dumps, only
incremental.

If your a small installation and don't mind doing one DLE at a
time, eliminate your holding disk.  Otherwise make it larger and
more useful.  I've currently got 3 holding disk pieces, totaling
about 120GB.  For a 9GB nightly run, that gives me lots of space
to hold dumps if I forget to change tapes.  Or it is broken as
it is now.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
 4455 Province Line Road        (609) 252-0159
 Princeton, NJ  08540-4322      (609) 683-7220 (fax)

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