NFSv4 delegation

[Sami Ketola]

Hi,

Just out of curiosity what is in nfsv4 delegation that you think would give a benefit on your configuration?

If I read back the thread you seem to have dovecot configured with director ring in front of the backends. In that case Dovecot already manages storage in a way that only one of the backends is accessing each users data at a time. So I can’t see anything but problems form enabling delegations.

Sorry but I have zero experience in running dovegot with nfsv4 delegations since in general it is not needed.

Sami

> On 18 Aug 2015, at 15:42, Alessio Cecchi <alessio at skye.it> wrote:
> 
> Hi,
> 
> last day I tried to enable "nfsv4 delegation" on my cluster (enable nfsv4.0 and read delegation on Netapp and remount the volume on Linux Centos 6.7 clients with Dovecot+Director).
> 
> It was a failure, after some minutes the load on clients was high, and in dovecot.log I found these errors (repeated continuously):
> 
> Aug 17 20:28:17 pop01eeh dovecot: imap(info at domain.com): Error: mail_index_wait_lock_fd() failed with file /home/domains/domain.com/info/Maildir/dovecot.index.log: Input/output error
> Aug 17 20:28:21 pop01eeh dovecot: imap(info at domain.com): Error: fcntl(/home/domains/domain.com/info/Maildir/dovecot.index.cache, write-lock, F_SETLKW) locking failed: Input/output error
> 
> Is really impossible to run NFSv4 with delegation with dovecot? If it were possible the number of NFS operations would drop so much with many benefits on performance.
> 
> Il 09/07/2015 17:08, brd ha scritto:
>> just a quick update:
>> 
>> no issues with NFSv4.0 (load is slowly growing, currently ~7k mailboxes)
>> 
>> instead, bad news from delegation front, we enabled it for a couple of
>> days but we ran in ugly issues: processes went in "uninterruptible
>> sleep" state, load average gets huge, reboot was the only escape :-(
>> 
>> -brd
>> 
>> Alessio Cecchi wrote:
>>> Il 12/06/2015 13:02, brd ha scritto:
>>>> Alessio Cecchi wrote:
>>>> [...]
>>>>> Have you already try to run NFSv4?
>>>> it's in place on a (very) small sample of mailboxes in dbox format, no issues
>>>> up to now (Debian Wheezy mainline kernel)
>>> 
>>> Good to know, let me know what will be when the load will grow.
>>> 
>>>>> When we switch to netapp and nfsv4 we had many problems (lock problems
>>>>> and instability) and we had to go immediately to NFSv3. I don't know if
>>>>> was a netapp problem or nfs client (Debian with 2.6 kernel), now we are
>>>>> using Centos 6 as NFS client and we should re-try to mount mailbox as nfsv4.
>>>> 
>>>> when you've had problems, the "delegation feature" was active on Netapp
>>>> filers? (AFAIK it is disabled by default)
>>> 
>>> Never enabled "delegation feature" on my netapp.
>>> 
>>> Probably my issue was on client side. I had to switch immediately to NFSv3
>>> without being able to investigate the problem.
>>> 
>>> Ciao
>>> --
>>> Alessio Cecchi
>>> http://www.linkedin.com/in/alessice
> 
> -- 
> Alessio Cecchi
> http://www.linkedin.com/in/alessice