Re: Looking for way to monitor dsync, confirm it is or isn't running

2016-03-13 Thread Rich Wales 
Earlier, I asked:

>> I would like to be able to run some sort of periodic health check to
>> confirm that dsync is (or is not) running properly between the two
>> sites, and alert me if dsync is failing or lagging excessively. Does
>> anyone know of a tool to do this?

and Michael Grimm replied:

> doveadm replicator status
> 
> If those numbers tend to become significantly larger than 0, then
> replication has issues. I do not use that for health checking . . .
> but used it once in a while when suspecting issues with replication.

Thanks.

As a followup question:  If "doveadm replicator status" shows problems,
are there any commands available to pinpoint exactly which request(s)
is/are causing the problem(s)?

One of the sites I am administering, for example, has been reporting
1 "queued 'full resync' requests" and 9 "waiting 'failed' requests" for
the past couple of days.  But I have no idea how to resolve the issue.
Suggestions welcome.

Rich Wales
ri...@richw.org

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread Stephan von Krawczynski 
On Mon, 14 Mar 2016 09:32:42 +1000
Noel Butler  wrote:

> On 13/03/2016 20:47, Stephan von Krawczynski wrote:
> > On Sun, 13 Mar 2016 09:45:06 +
> > James  wrote:
> > 
> >> On 11/03/2016 15:17, Stephan von Krawczynski wrote:
> >> 
> >>  > zfs set sync=disabled ?
> >> 
> >> Only if you are happy to loose data on power failure.
> > 
> > I don't know the actual setup, but if you have no UPC you shouldn't 
> > host email
> > services anyway.
> 
> I'm guessing you meant UPS, anyway, a UPS wont protect you from human 
> error.
> 
> Also, most buildings, at least in this country, have a fire emergency 
> shutoff requirement, meaning mains is isolated from the building, and 
> the back up gennies are also forbidden to be engaged - UPS's dont last 
> forever.

Guys, please don't argue on kindergarten level. The UPS is for backing a
sudden death, but not for running five days. Of course you can do a controlled
shutdown if battery level falls below a trigger value. And this is about all
you need: control. There is no fs error as long as you perform a regular
shutdown. If UPS-backup is forbidden in your country then I suggest moving to
civilized regions of the planet ;-)

-- 
Regards,
Stephan

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread Noel Butler 

On 13/03/2016 20:47, Stephan von Krawczynski wrote:

On Sun, 13 Mar 2016 09:45:06 +
James  wrote:


On 11/03/2016 15:17, Stephan von Krawczynski wrote:

 > zfs set sync=disabled ?

Only if you are happy to loose data on power failure.


I don't know the actual setup, but if you have no UPC you shouldn't 
host email

services anyway.


I'm guessing you meant UPS, anyway, a UPS wont protect you from human 
error.


Also, most buildings, at least in this country, have a fire emergency 
shutoff requirement, meaning mains is isolated from the building, and 
the back up gennies are also forbidden to be engaged - UPS's dont last 
forever.


--
If you have the urge to reply to all rather than reply to list, you best
first read  http://members.ausics.net/qwerty/

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread Stephan von Krawczynski 
On Sun, 13 Mar 2016 11:47:23 +0100
Stephan von Krawczynski  wrote:

> On Sun, 13 Mar 2016 09:45:06 +
> James  wrote:
> 
> > On 11/03/2016 15:17, Stephan von Krawczynski wrote:
> > 
> >  > zfs set sync=disabled ?
> > 
> > Only if you are happy to loose data on power failure.
> 
> I don't know the actual setup, but if you have no UPC you shouldn't host email
> services anyway.

That should read "UPS" of course ...

> -- 
> Regards,
> Stephan

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread Stephan von Krawczynski 
On Sun, 13 Mar 2016 09:45:06 +
James  wrote:

> On 11/03/2016 15:17, Stephan von Krawczynski wrote:
> 
>  > zfs set sync=disabled ?
> 
> Only if you are happy to loose data on power failure.

I don't know the actual setup, but if you have no UPC you shouldn't host email
services anyway.

-- 
Regards,
Stephan

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread James 

On 11/03/2016 15:17, Stephan von Krawczynski wrote:

> zfs set sync=disabled ?

Only if you are happy to loose data on power failure.

Re: NetApp NFS vs. ZFS and NFS for Maildir

2016-03-13 Thread James 

On 11/03/2016 14:58, Juan Bernhard wrote:


Someone has experiences with ZFS and NFS(v3) in high load environments?

Thanks


Be careful to no do any synchronous writes under ZFS.


By default all NFS writes are synchronous but I assume dovcot sync 
writes all data anyway so in this case the NFS sync doesn't matter.




Every sync write can take up to 3 seconds of latency (under freebsd,
I didnt test ZFS in linux).


sync writes should take a few ms (they do for me). If you have enough 
load for them to be a problem you should have enough revenue to afford 
an SSD as a ZFS write cache / SLOG and then they will no longer be a 
problem.