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List:       linux-lvm
Subject:    Re: [linux-lvm] Mirror fail/recover test
From:       malahal () us ! ibm ! com
Date:       2010-02-25 16:11:12
Message-ID: 20100225161112.GA14691 () us ! ibm ! com
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jose nuno neto [jose.neto@liber4e.com] wrote:
> Much thanks for your interest
> im putting more info below
> 
> > jose nuno neto [jose.neto@liber4e.com] wrote:
> >> Hi
> >>
> >> I'm trying to test the failure of a SAN Mirrored Lv, and the recover and
> >> check for data lost.
> >>
> >> Im runing RedHat 5.4
> >> 2.6.18-164.2.1.el5
> >> lvm2-2.02.46-8.el5_4.1
> 
> multipath -l -v2 | grep -A 7 3600a0b800048f9b200000c2b4b5980b7
> mpath12 (3600a0b800048f9b200000c2b4b5980b7) dm-8 SUN,CSM200_R
> [size=52G][features=1 queue_if_no_path][hwhandler=1 rdac][rw]
> \_ round-robin 0 [prio=0][enabled]
>  \_ 7:0:1:1  sdo  8:224  [active][undef]
>  \_ 9:0:1:1  sdq  65:0   [active][undef]
> \_ round-robin 0 [prio=0][enabled]
>  \_ 7:0:0:1  sdd  8:48   [active][undef]
>  \_ 9:0:0:1  sdf  8:80   [active][undef]
> 
> Before UnPluging
> dmsetup status mpath12
> 0 109051904 multipath 2 0 0 0 2 1 E 0 2 0 8:224 A 0 65:0 A 0 E 0 2 0 8:48
> A 0 8:80 A 0
> 
> echo offline > /sys/block/sdd/device/state
> echo offline > /sys/block/sdo/device/state
> echo offline > /sys/block/sdq/device/state
> echo offline > /sys/block/sdf/device/state
> 
> dmsetup status mpath12
> 0 109051904 multipath 2 0 0 0 2 1 E 0 2 0 8:224 F 1 65:0 F 1 E 0 2 0 8:48
> F 1 8:80 F 1

I was actually asking for "dmsetup status <mirror-device>" rather than
multipath device. I didn't know that you were using multipath devices!!!

Anyway, looks like you have mpath12 that probably queues I/O on path
failures rather than failing them back to upper layers. In other words,
if you were to run "dd" or any other app to mpath12, it would hang too.

mpath12 seems to keep the request and forever wait for the paths to
become available again in your case. If you really want it to fail,
configure your multipath accordingly.

Thanks, Malahal.
PS: "features=1 queue_if_no_path" in your 'multipath -ll' output is the
source of error here...

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