[Samba] Miserable read performance (factor ~60 too slow)

[Denis Vlasenko]

On Thursday 05 July 2007 00:48, Arno Schäfer wrote:
> - copying a 700MB file from the CIFS share of the Windows XP box to a 
> different Windows PC starts immediately and takes about two minutes.
> 
> - copying the same file via HTTP from the new Samba server takes a 
> little more than one minute (10.5 MB/sec).
> 
> - copying the file from the Samba share varies hugely. It can take 
> between 90 seconds and literally hours (!).
> 
> - sometimes it goes faster, but almost always the startup time is 
> between 20 and 90 seconds, that is the time before the copying even begins.
> 
> - I have found repeatedly that when I am copying a file from the Samba 
> share, and it goes extremely slow (estimated time 90 minutes), and I 
> start copying a second file (from the same or a different PC), suddenly 
> the copying speeds up to "normal" speed.

Run tcpdump and watch what is going on the wire. This very likely to give
more info: you will see retransmits, or data being sent in very small packets,
or big spans of nothing being sent...

strace -p <smbd process pid> can also be useful.
--
vda