On Mon, Mar 18, 2013 at 10:44 PM, Gene Heskett ghesk...@wdtv.com wrote:
On Monday 18 March 2013 10:06:59 Amit Karpe did opine:
Reply in-line:
On Mon, Mar 18, 2013 at 1:59 PM, Jon LaBadie j...@jgcomp.com wrote:
On Mon, Mar 18, 2013 at 12:55:40PM +0800, Amit Karpe wrote:
Brian,
Yes, initially I was using holdingdisk for all config. But when I
see backup is low and taking more time, I had doubt that my backup
holdingdisk are on same disk (NAS) which is 19TB. So I change it
force not to use it.
But now I realized its required so I will use for next usage of
Amanda.
Could someone let me know use of chunksize ?
It should big enough like 10GB or 50GB ?
As I am using Vtape, finally all these temporary files are going
to merge into one file. So why should we create these chunks ? Why
not
let
dumper directly dump into final vtape's slot directory ?
The holding disk chunksize was added to overcome the 2GB max file size
limitation of some filesystems. It is also useful if you allocate
multiple holding disks, some which may not be big enough for your
large DLEs.
The parts of amanda doing the dumps do not peek to see where the data
will eventually be stored. Taper does that part and it is not called
until a DLE is successfully dumped. If you are going direct to tape
taper is receiving the dump directly but then you can only do one DLE
at a time.
Jon
So using chunksize 10GB/ 50GB/ 100GB kind of option, will help amanda
to run dumper parallely ?
There are, generally speaking, several aspects of doing backups in
parallel.
1. If you don't want your disk(s) to be thrashed by seeking, and that of
course has a speed penalty, you must restrict the read operations to one
file at a time per disk spindle, this is in the docs, man disklist I
believe.
Yes, I got the idea. Will try in next backup process.
2. The chunk size is to get around some file system limits that often cause
things to go all aglay when fast integer math in the filesystem falls over
at 2Gb on a single file. It has nothing or very little to do with speed
other than the overhead of breaking it up during the writes to the holding
disk area, then splicing it back together as its sent down the cable to the
storage media. IOW it is to keep your OS from trashing the file as its
being put in the holding area as a merged file from the directory tree
specified in the disklist. IOW your file is likely not the problem
unless that file is a dvd image, but the merged output of tar or (spit)
dump, can easily be more than 2Gb.
I have one directory in my /home that will almost certainly have to be as
separate files as I have debian-testing for 3 different architectures here.
That would be about 30 disklist entries all by itself as there are 30 dvd
images for the whole thing.
Yes, now I am using Holding disk with big chunk size 100GB.
3. Parallelism would probably be helped, given that the data moving
bandwidth is sufficient, if more than one holding disk area was allocated,
with each allocation being on a separate spindle/disk so that the holding
disk itself would not be subjected to this same seek thrashing time killing
IF you also had more than one storage drive being written in parallel. If
only one tape is mounted at a time in your setup, once you've taken action
against seek thrashing of the source disk(s), the next thing is improving
the bandwidth.
Will try to use 2 holding disk in next backup process. And will udpate my
result here.
This last however, may not be something that amanda has learned how to use
effectively as AFAIK, there is not an optional 'spindle' number in the
holding disk entry for that distinction.
I am Not sure.
Cheers, Gene
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Regards
Amit Karpe.
http://www.amitkarpe.com/
http://news.karpe.net.in/
