[Samba] Re: Copying Files from XP to Samba (help needed)

[Peter Daum]

Unfortunately, running a packet sniffer on the server does not make
things any better in my case (otherwise it would be at least an
easy workaround ;)

Regards,
                    Peter Daum

Daniel Lindgren wrote:
> I am also having performance problems writing to a Samba share (see
> previous
> post about tcpdump) and I have seen a strange phenomenon: if I start
> tcpdump
> on the Samba machine, performance increases 20 times. It would be
> interesting to know if you also experience the same, just start tcpdump and
> redirect output to /dev/null while/before copying files.
> 
> Regards,
> Daniel Lindgren
> 
> 2006/10/9, Peter Daum <gator_ml at yahoo.de>:
>>
>> I am still desperately trying to figure out why I get such a horrible
>> performance trying to copy files from XP to Samba (below is my
>> original post to illustrate the context. Meanwhile, I found a
>> pretty remarkable pattern in the network traces.
>>
>> Generally, the packets send from the XP machine look like this:
>>
>> 01: WriteAndXRequest 60 kBytes (1392 bytes payload)
>> 02: 1460 bytes
>>     ...        (usual time delta between 2 packets < 0.0001 secs)
>> 42: 1460 bytes
>>     < < < < delta: 0.05 - 0.3 secs > > > >
>> 43: last 188 bytes
>> .. WriteAndXResponse from Samba machine, da capo
>>
>> It seems like what is slowing the transfer down so dramatically, is
>> the long gap before the last 188 bytes are sent. I can't see anything
>> reasonable the XP machine could be waiting for - it already got the
>> ack for the last preceding packet.
>>
>> To emphasize again, this is not a general networking problem between
>> the 2 machines; it only (at leas AFAIK) occurs  when copying large
>> files from Windows XP to Samba shares (and at that occasion I could
>> reproduce it with all the Samba servers and XP clients that I checked
>> so far)
>>
>> Any help would be greatly appreciated.
>>
>> Regards,
>>                              Peter Daum
>>
>> > I noted an extremely poor performance when copying big files from
>> > a windows xp client to a samba share. The exact version of samba
>> > does not seem to matter: I tried several different samba servers
>> > with versions between 3.014 and 3.0.23b running on Linux 2.4.32
>> > and 2.6.17 (machines and network otherwise idle, clients connected
>> > via fast ethernet, servers via Gbit; network performance in both
>> > directions around 95 Mbit/s). I made several tests copying a 1GB
>> > file with Windows 98 and Windows XP clients. Reading the file from
>> > the server takes predictably around 105 seconds (~9.75 MB/s).
>> >
>> > Writing to the server takes only slightly longer on Win98 (130
>> > seconds, ~8 MB/s) while the same takes approximately 45 minutes
>> > from a XP client (I don't know whether this matters, I noted that
>> > on the XP write test, the directory listing on the server
>> > immediately shows a file with the final size - obviously a sparse
>> > file, repeatedly invoking du shows the gradually increasing actual
>> > size).
>> >
>> > I wrote a little test program that just writes data to a file and
>> > shows the throughput; the transfer rates I get that way are pretty
>> > reasonable, so it is not a general problem but something that only
>> > occurs on specific operations like copying.
>> >
>> > Tracing the network traffic also didn't tell me what the problem
>> > might be: XP uses for copying as well as for other write
>> > operations WriteAndXRequest, the only peculiarity I noticed is the
>> > slightly exotic block size of 61440 bytes per request when copying
>> > (which also doesn't seem to be the problem - Win98 uses the same
>> > block size with WriteRaw)
>> >
>> > Has anybody else made similar experiences? (Since I could see this
>> > issue with differently configured servers/clients, it should not
>> > be just my personal problem. Of course in most settings where the
>> > data usually goes mostly from the server to the client it is not
>> > obvious)
>> >
>> > Any ideas what's going on and what to do about it?
>> >
>>
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