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Re: Amanda's planning for use of holding disk space
2009-07-01 13:42:55
Paul Bijnens wrote:
On 2009-06-30 19:52, Chris Hoogendyk wrote:
So, the question is, if Amanda has more than one holding disk
(partition), and they differ in size, will Amanda know when the
smaller one is inadequate for a particular DLE and explicitly choose
the larger one? Also, if I have specified spindle numbers in my
disklist, so that Amanda will avoid doing parallel dumps from the
same spindle, is there any way of informing Amanda of the spindle
numbers for the holding disks (partitions) and taking that into
account in the planning?
No problem at all.
You make config entry for each holdingdisk.
On each holdingdisk you can specify peculiarities of the disk,
like the path to the toplevel holdingdirectory, and the amount of
free space that should not be used etc.
Make sure to specify a chunksize that will fit easily on the smallest
disk. I make my chunksize 1GB.
Amanda will spread the holdingdisk data over all the holdingdisks
avoiding any problems when one DLE would not fit on a single area.
As side benefit you'll also get some improvement in throughput because
now taper reading finished dump images will compete less with the
dumpers writing to disk.
Making it different filesystems instead of one large logical volume makes
future adding/removing/swapping disks easier as well. And having
a disk error on one of the disks in raid0 lvm's is much worse
than on independent filesystems.
Also acknowledging Brian's comments.
A1: So, Amanda will make use of all the holding space available, and can
go across holding disks with a DLE if one fills up. That answers the
practical question regarding it simply working.
Q2: I presume then, since Paul & Brian have spoken up, and no one has
mentioned it, that Amanda has no understanding of spindle numbers with
regard to holding disk space. So, it will just be chance that determines
whether a DLE, that happens to be on the same spindle as one of the
holding disk partitions, gets dumped to that particular holding disk
partition. Of course, this is then the disadvantage of using a partition
on a shared disk rather than dedicating the whole disk for holding
space. And, on those systems where I have the luxury, I have configured
two whole disks as two separate holding disk spaces.
Q3: This does still leave a choice. If I can only manage one disk's
worth of space, should I go through the effort of rearranging existing
partitions in order to shuffle space and get one dedicated disk for
holding disk space? The question is whether one dedicated disk will lead
to better efficiency than multiple holding partitions spread across a
few shared disk drives (where a DLE and a holding space may be on the
same spindle). I would have all dumps going to the same spindle, but it
would never be the same spindle that a DLE was being dumped from.
And, for those who mentioned it -- No, I won't be using LVM. For one
thing, this isn't Linux. For another, it is a legacy system with lots of
drives and partitions that have all been assigned for their own
particular uses and needs. On my newer systems, I'm using ZFS (which
obsoletes other volume managers), but I'm still keeping Amanda holding
disks as separate dedicated disk drives with UFS. This guarantees no
issues with i/o contention or bandwidth.
--
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Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<hoogendyk AT bio.umass DOT edu>
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Erdös 4
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