Re: NFSv4 and Maildir

[Joseph Tam]

Noel Butler writes:


I found the same thing, and turning off write delegation seemed
to have solved the problem.  I still don't know why, though.


write delegation is disabled by default on NetApp with v4, or have they
changed this now?


I think this is still the case: when I exported NFSv4, I also turned on
both r/w delegation as well.  The exported filesystem exhibited weird
locking or slow write operations on NFS clients (e.g. "touch newfile"
would take a second to complete).  This went away when I turned off
write delegation.

Joseph Tam 

Re: NFSv4 and Maildir

[Noel Butler]

On 01/10/2016 08:27, Joseph Tam wrote:

we have a setup with (CentOS 6) Director+Dovecot, Maildir as storage 
on

NetApp NFS v3. Every time I try to switch to NFS v4 I found issue with
lock (and others). So for me NFSv4 with Maildir is "unstable" or need 
a

fine tuning that I don't know.


I found the same thing, and turning off write delegation seemed
to have solved the problem.  I still don't know why, though.

Joseph Tam <jtam.h...@gmail.com>


write delegation is disabled by default on NetApp with v4, or have they 
changed this now?

0x7FD036C7.asc
Description: application/pgp-keys

Re: NFSv4 and Maildir

[Joseph Tam]

we have a setup with (CentOS 6) Director+Dovecot, Maildir as storage on
NetApp NFS v3. Every time I try to switch to NFS v4 I found issue with
lock (and others). So for me NFSv4 with Maildir is "unstable" or need a
fine tuning that I don't know.


I found the same thing, and turning off write delegation seemed
to have solved the problem.  I still don't know why, though.

Joseph Tam <jtam.h...@gmail.com>

Re: NFSv4 and Maildir

[Alessio Cecchi]

Il 23/09/2016 14:31, Robert Blayzor ha scritto:

Recently moving to newer storage platforms for mailbox storage so looking at 
moving mounts from NFSv3 with lots of issues with locking and caching to NFSv4.

There seems to be a lot of benefits to v4 along with some other new features, 
namely “delegation”.

So the question boils down to, to delegate or not delegate on Maildir storage. 
There may be many reasons based on actual platform why to do (or not to do 
this), but I want to get the general opinion from others that may have more 
experience with this. Our setup is several FreeBSD 10.x clients running 
Dovecot/Exim, NetApp NFS mail storage (probably moving to TrueNAS) and using F5 
load balancers for client side connections/SSL offload.

From what I’ve found (and what i’ve read in the RFC) is that delegation seems 
to work best when there is NOT a lot of file contention from clients accessing 
the same files. I realize that in some situations many people are using 
director to try and keep users on the same client; in our case we’re doing it 
with F5 iRules. The F5 iRules work great for POP3 and IMAP session persistence, 
but unfortunately that doesn’t work for SMTP and Dovecot LDA, so we still have 
possible race conditions from the MTA’s delivering into “INBOX”. (mostly 
dovecot indexes updating at the same time).

So the big question is, who is using Dovecot with maildirs with NFSv4 mounts. 
What has your experience been? Are you using delegation?  By choice and why did 
you come to that decision.

I’m drawing up the conclusion that if you can *mostly* control client control 
to specific files (ie: directing access to a mailbox to come from one client), 
then delegation might be ok. However, if you’re not using director and have 
several NFS mail clients racing to access mailboxes, then delegation might turn 
into chaos.


Your comments welcome and appreciated.


Hi Robert,

we have a setup with (CentOS 6) Director+Dovecot, Maildir as storage on 
NetApp NFS v3. Every time I try to switch to NFS v4 I found issue with 
lock (and others). So for me NFSv4 with Maildir is "unstable" or need a 
fine tuning that I don't know.


--
Alessio Cecchi
Postmaster @ http://www.qboxmail.it
https://www.linkedin.com/in/alessice

NFSv4 and Maildir

[Robert Blayzor]

Recently moving to newer storage platforms for mailbox storage so looking at 
moving mounts from NFSv3 with lots of issues with locking and caching to NFSv4.

There seems to be a lot of benefits to v4 along with some other new features, 
namely “delegation”.

So the question boils down to, to delegate or not delegate on Maildir storage. 
There may be many reasons based on actual platform why to do (or not to do 
this), but I want to get the general opinion from others that may have more 
experience with this. Our setup is several FreeBSD 10.x clients running 
Dovecot/Exim, NetApp NFS mail storage (probably moving to TrueNAS) and using F5 
load balancers for client side connections/SSL offload.

From what I’ve found (and what i’ve read in the RFC) is that delegation seems 
to work best when there is NOT a lot of file contention from clients accessing 
the same files. I realize that in some situations many people are using 
director to try and keep users on the same client; in our case we’re doing it 
with F5 iRules. The F5 iRules work great for POP3 and IMAP session persistence, 
but unfortunately that doesn’t work for SMTP and Dovecot LDA, so we still have 
possible race conditions from the MTA’s delivering into “INBOX”. (mostly 
dovecot indexes updating at the same time).

So the big question is, who is using Dovecot with maildirs with NFSv4 mounts. 
What has your experience been? Are you using delegation?  By choice and why did 
you come to that decision.

I’m drawing up the conclusion that if you can *mostly* control client control 
to specific files (ie: directing access to a mailbox to come from one client), 
then delegation might be ok. However, if you’re not using director and have 
several NFS mail clients racing to access mailboxes, then delegation might turn 
into chaos.


Your comments welcome and appreciated.

--
Robert
inoc.net!rblayzor
XMPP: rblayzor.AT.inoc.net
PGP Key: 78BEDCE1 @ pgp.mit.edu