Vicki:
The reserve percentage works this way, as I understand it. Someone please
correct me if I have the details wrong:
The "reserve" setting is the amount of "available holding disk" to hold back
to do degraded mode incremental dumps if Amanda cannot write to a tape.
For example, say you have a 50 GB holding disk and your "reserve" setting is
50 (for 50 percent reserved).
If you start out the day with all 50 GB of holding disk free, then it will
"reserve" one-half of the disk for incremental dumps in degraded mode.
Amanda will schedule up to 25 GB of level-0 dumps if the tape is not
available.
If you start the next day with 30 GB of holding disk free and the same
"reserve" setting of 50, then Amanda will schedule up to 15 GB of level-0
dumps for the day, reserving the other 15 GB for incremental dumps in
degraded mode.
So, the "reserve" setting is the amount of "available holding disk" to hold
back to do degraded mode incremental dumps if the tape drive is not
accessible or there is no available Amanda tape (for example, if you forgot
to change the tape before Amanda ran today). Note that the percent is
against the available storage, so if your reserve percentage is less than
100 percent (the default), then Amanda will try to use that amount of
holding disk for level-0 dumps each day.
Note also that the default for "reserve" is 100 percent, which translates to
Amanda skipping any full dumps in degraded mode. Depending on the amount of
space you have devoted to holding disk, this may or may not work well for
you.
Questions?
Don
Donald L. (Don) Ritchey
Information Technology
Exelon Corporation
-----Original Message-----
From: Vicki Stanfield [mailto:vicki AT progeny DOT com]
Sent: Wednesday, January 19, 2005 3:14 PM
To: amanda-users AT amanda DOT org
Subject: Re: Data loss if configuration of amanda.conf is not right.
On Wed, 2005-01-19 at 10:38 -0500, Jon LaBadie wrote:
> On Wed, Jan 19, 2005 at 09:57:22AM -0500, Vicki Stanfield wrote:
> >
> > Thanks. I was unsure of whether this was a potential problem or not. As
> > long as Amanda tells me that there was a problem and dumps to the spool,
> > I am happy.
>
> Make sure your "holding disk" space is sufficiently large and
> that your "reserve" parameter is set to some value smaller
> than the default 100%. The reserve aspect is to reserve the
> holding disk for incrementals only when there are tape drive
> problems. If your holding disk is sufficiently large, you
> can also hold some full backups so the reserve should be
> decreased. I have enough holding disk for several days
> of normal dumps (> 1wk) and use a reserve of 20%.
>
> jl
I'm not sure that I correctly understand the reserve parameter. I have
heard that it is used to get amanda to degrade full dumps to merely
incremental dumps if the holding disk gets full. I assume the percentage
refers to how full. So how does degrading to incrementals help if the
holding disk is 100% full? What am I misunderstanding here? I can
understand saying that if the holding disk is 75% full, switch to
incrementals though.
Vicki
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