On Fri, Jan 05, 2018 at 11:23:49AM -0800, Chris Miller wrote:
> Hi Jean-Louis,
>
> | runtapes 1 # number of tapes to be used in a single run of amdump
>
> | Because you tell it to use one tape.
> As advertised, Amanda behaviors that I don't yet understand...
>
> So, I suspect that vtape behavior is a big piece of Amanda and from this low
> point on the learning curve, it looks formidable. Is there some document that
> describes it sufficiently that I don't have to make a lot of mistakes and ask
> a lot of stupid questions?
>
> So, having been so helpful with that question, I have two more:
>
> 1. If I am backing up a client to a NAS appliance, then I don't see how
> it makes sense to have a holding disk, so I think I want to configure that
> out. Am I right?
No you are not.
Amanda does not just store backups on random access devices. Some
amanda sites still use real tape. The core sections of amanda are
written to be storage device agnostic. With real tape, only one
DLE can have its backup being written to the storage device at a
time. If a backups are written directly to the storage device each
DLE will have to wait its sequential turn.
In my small environment, 6 hosts and 25 DLEs, that could take as long
as 10+ hours ('Dump Time' in the daily report). Yet the longest the
entire run has taken has been 3.5 hours ('Run Time'). That is the
first benefit of a local random access device, called a holding disk,
to collect DLE dumps before sending them to the storage device. The
holding disk can be collecting multiple simultaneous dumps, even while
sending a previously completed dump to the storage device.
I configure my setup to allow a maximum of 4 simultaneous dumps, not
more than 2 from the same host or disk spindle.
Perhaps, though I doubt it, you are fortunate enough to never have
your connection to the NAS down. That is a second benefit of a
holding disk. Where do you put backups when the storage device is
not available? My holding disk is sufficiently large to save 2-5
days worth of normal backups. For extended outages, when holding
disk space gets tight, amanda switches to doing only incrementals.
BTW the normal amanda recovery tools know if a backup is on the
holding disk or on the storage device and can do recoveries from
either.
So yes, you can run amanda without a holding disk. But I wouldn't.
Jon
--
Jon H. LaBadie j...@jgcomp.com
11226 South Shore Rd. (703) 787-0688 (H)
Reston, VA 20190 (703) 935-6720 (C)
