[dm-crypt] trouble with dm-crypt and NFS: server hangs

Arno Wagner arno at wagner.name
Thu Mar 27 21:28:33 CET 2014


Thank you!

Arno

On Thu, Mar 27, 2014 at 18:56:06 CET, Stephen Cousins wrote:
> I'm following up on this to let you know that it has been identified as a
> ZFS sync issue that has been addressed recently. No need to contact
> dm-devel.
> 
> Thanks for your help.
> 
> Steve
> 
> 
> On Thu, Mar 20, 2014 at 6:12 PM, Stephen Cousins <steve.cousins at maine.edu>wrote:
> 
> > I'm getting mixed results but it is looking like ZFS have something to do
> > with the problem afterall.
> >
> > I tried it with dm-crypt -> XFS -> NFS and I'm not seeing the same lag
> > issue. I say mixed results mainly because I've been using rsync to do the
> > testing and for some reason rsync has trouble with this setup. It works but
> > really slowly. Like around 3 MB/sec over a Gigabit link. If I use "cp -pR"
> > then it goes at 60 MB/sec. I use rsync all the time and I've never seen
> > this before so it took a while for me to realize that rsync was acting up.
> > Anyone run into this before?
> >
> > I'll bring this to the ZFSonLinux people and see what they say.
> >
> > Thanks,
> >
> > Steve
> >
> >
> > On Thu, Mar 20, 2014 at 3:16 PM, Milan Broz <gmazyland at gmail.com> wrote:
> >
> >> On 03/20/2014 03:48 PM, Stephen Cousins wrote:
> >> > I am testing dm-crypt with a system that serves data over NFS. I'm
> >> > finding that when serving the data over NFS4 it will go for a little
> >> > while and then it will just stop copying and networking on the NFS
> >> > server will stall out so that other connections to other parts of the
> >> > storage (a non-dm-crypt volume) will become very laggy. Soon after
> >> > canceling the copy the other connections resume back to normal.
> >> >
> >> > I have tried this on two different servers, one with a single disk
> >> > with ZFS and another with a ZFS raidz2 pool and they both do the same
> >> > thing. CPU doesn't seem to be an issue. Doing local copies is not a
> >> > problem. That is, copying to/from these volumes made up of dm-crypted
> >> > disks from other disks on the server have no problems.
> >> >
> >> > One system (the one with the RAID pool) is CentOS 6.4 and the other
> >> > one is CentOS 6.5.
> >> >
> >> > I'm curious if anyone else has run into this before and if so, what
> >> > can be done to make it work? I'm going to test to see if taking ZFS
> >> > out of the equation helps. I haven't run into this with ZFS with
> >> > disks without dm-crypt.
> >>
> >> Hi,
> >>
> >> unfortunately the dmcrypt code in Centos 6.x is not what is upstream
> >> kernel (mainly because of per cpu processing changes upstream).
> >> (It would be interesting if it is reproducible with upstream kernel,
> >> but I guess it is not easy to test...)
> >>
> >> I am adding cc to dm-devel list, maybe someone there could have some idea
> >> how to help here.
> >>
> >> Milan
> >>
> >> >
> >> > Thanks,
> >> >
> >> > Steve
> >> >
> >> >
> >> >
> >> > -- ________________________________________________________________
> >> > Steve Cousins             Supercomputer Engineer/Administrator
> >> > Advanced Computing Group            University of Maine System 244
> >> > Neville Hall (UMS Data Center)              (207) 561-3574
> >> > <tel:%28207%29%20561-3574> Orono ME 04469
> >> > steve.cousins at maine.edu <http://maine.edu>
> >>
> >
> >
> >
> > --
> > ________________________________________________________________
> >  Steve Cousins             Supercomputer Engineer/Administrator
> >  Advanced Computing Group            University of Maine System
> >  244 Neville Hall (UMS Data Center)              (207) 561-3574
> >  Orono ME 04469                      steve.cousins at maine.edu
> >
> >
> 
> 
> -- 
> ________________________________________________________________
>  Steve Cousins             Supercomputer Engineer/Administrator
>  Advanced Computing Group            University of Maine System
>  244 Neville Hall (UMS Data Center)              (207) 561-3574
>  Orono ME 04469                      steve.cousins at maine.edu

> _______________________________________________
> dm-crypt mailing list
> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt


-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -  Plato


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