[dm-devel] Device Mapper MultiPath

Thu Apr 2 21:58:03 UTC 2009

I can reproduce Andy's multipathd behaviour with scsi_debug (symmetrix arrays too)... only with the upstream directio checker. My guess is that the async code in there misbehaves. Needs review.

----- Mail Original -----
De: "Andy" <genanr at emsphone.com>
À: "device-mapper development" <dm-devel at redhat.com>
Envoyé: Jeudi 2 Avril 2009 23h50:08 GMT +01:00 Amsterdam / Berlin / Berne / Rome / Stockholm / Vienne
Objet: Re: [dm-devel] Device Mapper MultiPath

On Thu, Apr 02, 2009 at 03:32:33PM -0400, Konrad Rzeszutek wrote:
> On Thu, Apr 02, 2009 at 02:09:56PM -0500, Andy wrote:
> > On Wed, Apr 01, 2009 at 04:31:08PM -0400, Konrad Rzeszutek wrote:
> > > On Wed, Apr 01, 2009 at 03:08:41PM -0500, Andy wrote:
> > > > On Tue, Mar 31, 2009 at 08:25:59PM -0400, Konrad Rzeszutek wrote:
> > > > > On Tue, Mar 31, 2009 at 09:07:08PM -0300, Rodrigo Nascimento wrote:
> > > > > > Hi All,
> > > > > > 
> > > > > > I'm a student of computer sciences and I'd like to collaborate with the
> > > > > > development of the DM-MP.
> > > > > > I know that maybe you received this kind of message during all time, but I
> > > > > 
> > > > > I think you are the first :-)
> > > > > 
> > > > > > really want to help, with anything.
> > > > > 
> > > > > Shakedown help would be nice. As in, trying to yank stuff underneath it, 
> > > > > add new block disks, remove them, add them, remove them, edit the
> > > > > multipath.conf file and issue 'reconfigure', resize the maps, 
> > > > > then add 1000+LUNs, and while they are being added, start removing the
> > > > > LUNs, then for extra fun call 'dmsetup remove_all' while in another
> > > > > thread you run 'multipath'. Ooh, and see if there are any memory leaks
> > > > > while this all is being done.
> > > > > 
> > > > 
> > > > What I would really like to see is online resizing of non-partitioned dm
> > > > block devices.  I would love to be able to resize an underlying dm-mp block
> > > > device, and the just grow the filesystem without using a extra, un-needed,
> > > 
> > > Benjamin posted a CVS patch of this, that I've forward-ported to work with
> > > the latest git. It is attached.
> > > 
> > > 
> > 
> > Thanks, I must have missed that post.  Unfortantly, I am having problems with
> > multipathd in the latest git.  It fails all my paths and hangs.  It I go
> 
> Ugh. That doesn't bode well. Try running it with 'strace' to see if it is hanging
> on the ioctl or what not.
> 

The multipathd process is just sitting there polling, but I don't think it
gets to a point where it can handle requests from an interactive version of
itself.

I do see detecting or failing the paths in the log:

Apr 02 16:24:01 | sdc: ownership set to test1_vm1
Apr 02 16:24:01 | sdc: not found in pathvec
Apr 02 16:24:01 | sdc: mask = 0xc
Apr 02 16:24:01 | sdc: path checker = directio (controller setting)
Apr 02 16:24:01 | sdc: state = running
Apr 02 16:24:01 | directio: starting new request
Apr 02 16:24:01 | directio: async io getevents returns -14 (errno=No such file or directory)
Apr 02 16:24:01 | directio: abort check on timeout
Apr 02 16:24:01 | sdc: state = 2
Apr 02 16:24:01 | sdc: checker msg is "directio checker reports path is down"
Apr 02 16:24:01 | sde: ownership set to test1_vm1
Apr 02 16:24:01 | sde: not found in pathvec
Apr 02 16:24:01 | sde: mask = 0xc
Apr 02 16:24:01 | sde: path checker = directio (controller setting)
Apr 02 16:24:01 | sde: state = running
Apr 02 16:24:01 | directio: starting new request
Apr 02 16:24:01 | directio: async io getevents returns -14 (errno=No such file or directory)
Apr 02 16:24:01 | directio: abort check on timeout
Apr 02 16:24:01 | sde: state = 2
Apr 02 16:24:01 | sde: checker msg is "directio checker reports path is down"
Apr 02 16:24:01 | test1_vm1: pgfailover = -1 (internal default)
Apr 02 16:24:01 | test1_vm1: pgpolicy = multibus (LUN setting)
Apr 02 16:24:01 | test1_vm1: selector = round-robin 0 (LUN setting)
Apr 02 16:24:01 | test1_vm1: features = 0 (controller setting)
Apr 02 16:24:01 | test1_vm1: hwhandler = 0 (controller setting)
Apr 02 16:24:01 | test1_vm1: rr_weight = 1 (controller setting)
Apr 02 16:24:01 | test1_vm1: minio = 1 (LUN setting)
Apr 02 16:24:01 | test1_vm1: no_path_retry = NONE (internal default)
Apr 02 16:24:01 | pg_timeout = NONE (internal default)
Apr 02 16:24:01 | test1_vm1: set ACT_NOTHING (no usable path)
Apr 02 16:24:01 | sdb: ownership set to u01_vm1
Apr 02 16:24:01 | sdb: not found in pathvec
Apr 02 16:24:01 | sdb: mask = 0xc
Apr 02 16:24:01 | sdb: path checker = directio (controller setting)
Apr 02 16:24:01 | sdb: state = running
Apr 02 16:24:01 | directio: starting new request
Apr 02 16:24:01 | directio: async io getevents returns -14 (errno=No such file or directory)
Apr 02 16:24:01 | directio: abort check on timeout
Apr 02 16:24:01 | sdb: state = 2
Apr 02 16:24:01 | sdb: checker 

Other than that, I did not see anything significant in the strace or the
debugging messages.

Andy

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