[Samba] 1 byte writes

[Thomas Limoncelli]

After migrating a particular W2K file service to Samba 3.0.21c on SuSE 
9.3 Pro (a DMS with winbindd against a W2K3 ADS), the W2K clients are 
suffering performance issues (in a switched LAN).

Looking at the traffic with Ethereal (latest SVN), it looks like the 
client writes the data in *1 byte* pieces likes this (c=client, s=server):

c->s NT Create AndX Request
c<-s NT Create AndX Response
c->s Trans2 Request, SET_FILE_INFO
c<-s Trans2 Response
c->s Trans2 Request, QUERY_FILE_INFO, Query File Basic Info (1004)
c<-s Trans2 Response
c->s Write AndX Request, 1 byte at offset 119  <-- sigh
c<-s Write AndX Response, 1 byte
c->s Trans2 Request, QUERY_FILE_INFO, Query File Standard Info (258)
c<-s Trans2 Response
c->s Write AndX Request, 1 byte at offset 155  <-- sigh again
c<-s Write AndX Response, 1 byte
c->s Trans2 Request, QUERY_FILE_INFO, Query File Standard Info (258)
c<-s Trans2 Response
c->s Write AndX Request, 1 byte at offset 191  <-- see above
c<-s Write AndX Response, 1 byte
...
c->s Write AndX Request, 1 byte at offset 6629781  <-- 100 secs later!!
c<-s Write AndX Response, 1 byte
c->s Trans2 Request, QUERY_FILE_INFO, Query File Standard Info (258)
c<-s Trans2 Response
c->s Write AndX Request, 4096 bytes at offset 0  <-- the file header?
c<-s Write AndX Response, 4096 bytes
c->s Write AndX Request, 2454 bytes at offset 6627328  <-- strange
c<-s Write AndX Response, 2454 bytes
c->s Flush Request
c<-s Flush Response
c->s Close Request
c<-s Close Response

resulting in incredibly poor write performance. Does this ring a bell 
with anyone?

Searching the list archives, this issue seems to be only known with 
particular poorly-written applications:

http://groups.google.com/group/mailing.unix.samba/browse_thread/thread/89c619c8ea1e48/256e1ebf227819cc

but we're running none of those mentioned there (but may have found yet 
another ;-)).

Then, still, there haven't been any noticeable performance issues with 
the same application against the original W2K file server, so /me ends 
up as the one being pointed at. :-(

smb.conf global settings are the same as in an earlier thread 
(http://lists.samba.org/archive/samba/2006-February/118057.html) plus 
the following share-level settings:

[grp$]
         path = /cifs/grp
         valid users = +XXX\mygroup
         read only = No
         create mask = 0770
         directory mask = 0770
         nt acl support = Yes
         acl group control = Yes
         map acl inherit = Yes


Any ideas?


-TL