Hello,

13.10.2009 14:27, justAck wrote:
> Arno,
> 
> 
> Arno Lehmann wrote:
>> ...
>>> a) result file will be most likely not fragmented on disk at all
>> This is most likely in the situation you outline.
>> ...
>>
>> The most common reasons for slow restores, in my experience, are
>> ...
>>
> 
> Thanks for quick and useful help.
> I meant file access _after_ it is restored, not restore speed. 

Ok... that's quite a different thing.

> I need to do some more tests, but it looks that just
> cp /restored/file > /dev/null 
> is performed 20% slower speed than copying of other files. 

This is very interesting... I doubt that Bacula can be the cause for 
this. It seems possible, though, that very shortly after a large set 
of files was restored, the buffers and cache are occupied by the files 
last restored and thus access to other files can be slower. But that 
should only be a temporary problem. I don't really believe that... in 
other words, I have no idea what could cause the behaviour you observe.

> Doesn't bacula have some "image backup" format, when raw filesystem is
> copied and then restored back? (This is only situation I can imagine which
> keeps file fragmentation).

Bacula has no special feature to do that, though you can back up raw 
partitions and restore those images, but then the fragmentation would 
be exactly the same as before - and I doubt that raw partition back up 
is used very often as it tends to waste space.

> Maybe some cache is involved, need to test deeper, just wanted feedback
> about possible scenarios.

See above - I'd try vmstat 1 during a restore and subsequent read 
performance test, then wait a while, and do a nother read performance 
test.

Arno

> Thanks again!

-- 
Arno Lehmann
IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück
www.its-lehmann.de

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