fsync() takes about 0.06 second ---makes Cyrus deliver slow

[Su Li]

Daniel,

My Linux is red hat 7.2-1 with kernel 2.4.7-10. The file system is ext3.
Hard disk it RAID5. 

Jure, 
Thanks for your configuration. I 'll give a try and post my result to the
new group.

David,
I tried remove suppression from /etc/cyrus.conf. The suppression is still
there. Maybe I should try remove it from the code.


-----
Besides, I did some calculation on the time of the system calls on a
new-email. 3 fcync takes about 0.15 seconds. Each mail overall takes 0.65
seconds. I see the number of locks and deliver process can go up to
thousands. Maybe some thing else is also taking big time, say the
communication between deliver and lmtpd? 

Anyway, I'll keep trying. Thanks for every body's help. If anybody got some
idea, please let me know.


Su     


 

-----Original Message-----
From: Robert Scussel [mailto:rscuss at omniti.com]
Sent: September 9, 2002 4:58 PM
To: Su Li
Cc: 'Jure Pecar'; info-cyrus at lists.andrew.cmu.edu
Subject: Re: fsync() takes about 0.06 second ---makes Cyrus deliver slow


Depending on how consistent you want your data, you can always define 
your own fsync which can do nothing and then call sync directly from 
somewhere else. This is however dangerous, as you could experience file 
corruption.

Out of curiousity, what fs/OS are you using? We have noted this as a 
major factor of fsync times.

B

Su Li wrote:
> Thanks Jure,
> 
> I asked my system adm. He said I could change the hard disk to RAID1+0
which
> can problely give me 2 time faster. And I have put /spool/imap/user in a
> seprate disk already. Even if times 2, I can only get 2-3 emails per
second.
> I have 15,000 users on the server. That is still slow. 
> 
> 
> 
> Su
> 
> -----Original Message-----
> From: Jure Pecar [mailto:pegasus at telemach.net]
> Sent: September 9, 2002 4:27 PM
> To: Su Li
> Cc: info-cyrus at lists.andrew.cmu.edu
> Subject: Re: fsync() takes about 0.06 second ---makes Cyrus deliver slow
> 
> 
> On Mon, 9 Sep 2002 16:00:28 -0400 
> Su Li <sli at rim.net> wrote:
> 
> 
>>I wonder is there any way to may fsync() faster? If not is there any way
>>to call fsync less often? Will using a fast hard disk help? Or will move
>>the mail store -- /spool/imap/user to a database help?
> 
> 
> For what i know, fsync() speed is directly poportional to the speed of
your
> disks (avg. access time more than r/w speed). The most you can do is to
keep
> different cyrus files on differet physical disks, possibly on differnet
raid
> arrays. Remember, mail means lots of fsync()s means disk being the
> bottleneck. If you really need the performance, check some of the solid
> state disks available around the net. 
> 
> 
> --
> 
> 
> Jure Pecar
> 



-- 
Robert Scussel
1024D/BAF70959/0036 B19E 86CE 181D 0912  5FCC 92D8 1EA1 BAF7 0959