10:51 a.m.
Hi
We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct Luns for
all our VMs.
At the weekend during early hours an Equallogic controller failed over to
its standby on one of our arrays and this caused about 20 of our VMs to be
paused due to IO problems.
I have also noticed that this happens during Equallogic firmware upgrades
since we moved onto Ovirt 3.65.
As recommended by Dell disk timeouts within the VMs are set to 60 seconds
when they are hosted on an EqualLogic SAN.
Is there any other timeout value that we can configure in vdsm.conf to stop
VMs from getting paused when a controller fails over ?
Also is there anything that we can tweak to automatically unpause the VMs
once connectivity with the arrays is re-established ?
At the moment we are running a customized version of storageServer.py, as
Ovirt has yet to include iscsi multipath support for Direct Luns out of the
box.
Many Thanks
*Gary Lloyd*
________________________________________________
I.T. Systems:Keele University
Finance & IT Directorate
Keele:Staffs:IC1 Building:ST5 5NB:UK
+44 1782 733063 <%2B44%201782%20733073>
________________________________________________
7:03 p.m.
On 4 Oct 2016, at 09:51, Gary Lloyd <g.lloyd(a)keele.ac.uk>
wrote:
Hi
We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct Luns for all our VMs.
At the weekend during early hours an Equallogic controller failed over to its standby on
one of our arrays and this caused about 20 of our VMs to be paused due to IO problems.
I have also noticed that this happens during Equallogic firmware upgrades since we moved
onto Ovirt 3.65.
As recommended by Dell disk timeouts within the VMs are set to 60 seconds when they are
hosted on an EqualLogic SAN.
Is there any other timeout value that we can configure in vdsm.conf to stop VMs from
getting paused when a controller fails over ?
not really. but things are not so different when you look at it from the guest
perspective. If the intention is to hide the fact that there is a problem and the guest
should just see a delay (instead of dealing with error) then pausing and unpausing is the
right behavior. From guest point of view this is just a delay it sees.
Also is there anything that we can tweak to automatically unpause the VMs once
connectivity with the arrays is re-established ?
that should happen when the storage domain monitoring detects error and then
reactivate(http://gerrit.ovirt.org/16244). It may be that since you have direct luns it’s
not working with those….dunno, storage people should chime in I guess...
Thanks,
michal
At the moment we are running a customized version of storageServer.py, as Ovirt has yet
to include iscsi multipath support for Direct Luns out of the box.
Many Thanks
Gary Lloyd
________________________________________________
I.T. Systems:Keele University
Finance & IT Directorate
Keele:Staffs:IC1 Building:ST5 5NB:UK
+44 1782 733063
________________________________________________
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
9:22 p.m.
On Tue, Oct 4, 2016 at 7:03 PM, Michal Skrivanek <
michal.skrivanek(a)redhat.com> wrote:
> On 4 Oct 2016, at 09:51, Gary Lloyd <g.lloyd(a)keele.ac.uk> wrote:
>
> Hi
>
> We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct Luns for
all our VMs.
> At the weekend during early hours an Equallogic controller failed over
to its standby on one of our arrays and this caused about 20 of our VMs to
be paused due to IO problems.
>
> I have also noticed that this happens during Equallogic firmware
upgrades since we moved onto Ovirt 3.65.
>
> As recommended by Dell disk timeouts within the VMs are set to 60
seconds when they are hosted on an EqualLogic SAN.
>
> Is there any other timeout value that we can configure in vdsm.conf to
stop VMs from getting paused when a controller fails over ?
not really. but things are not so different when you look at it from the
guest perspective. If the intention is to hide the fact that there is a
problem and the guest should just see a delay (instead of dealing with
error) then pausing and unpausing is the right behavior. From guest point
of view this is just a delay it sees.
>
> Also is there anything that we can tweak to automatically unpause the
VMs once connectivity with the arrays is re-established ?
that should happen when the storage domain monitoring detects error and
then reactivate(http://gerrit.ovirt.org/16244). It may be that since you
have direct luns it’s not working with those….dunno, storage people should
chime in I guess...
We don't monitor direct luns, only storage domains, so we do not support
resuming vms using direct luns.
multipath does monitor all devices, so we could monitor the devices status
via multipath, and resume paused vms when a device move from faulty
state to active state.
Maybe open an RFE for this?
Nir
9:11 p.m.
On Tue, Oct 4, 2016 at 10:51 AM, Gary Lloyd <g.lloyd(a)keele.ac.uk> wrote:
Hi
We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct Luns for
all our VMs.
At the weekend during early hours an Equallogic controller failed over to
its standby on one of our arrays and this caused about 20 of our VMs to be
paused due to IO problems.
I have also noticed that this happens during Equallogic firmware upgrades
since we moved onto Ovirt 3.65.
As recommended by Dell disk timeouts within the VMs are set to 60 seconds
when they are hosted on an EqualLogic SAN.
Is there any other timeout value that we can configure in vdsm.conf to
stop VMs from getting paused when a controller fails over ?
You can set the timeout in multipath.conf.
With current multipath configuration (deployed by vdsm), when all paths to
a device
are lost (e.g. you take down all ports on the server during upgrade), all
io will fail
immediately.
If you want to allow 60 seconds gracetime in such case, you can configure:
no_path_retry 12
This will continue to monitor the paths 12 times, each 5 seconds
(assuming polling_interval=5). If some path recover during this time, the io
can complete and the vm will not be paused.
If no path is available after these retries, io will fail and vms with
pending io
will pause.
Note that this will also cause delays in vdsm in various flows, increasing
the chance
of timeouts in engine side, or delays in storage domain monitoring.
However, the 60 seconds delay is expected only on the first time all paths
become
faulty. Once the timeout has expired, any access to the device will fail
immediately.
To configure this, you must add the # VDSM PRIVATE tag at the second line of
multipath.conf, otherwise vdsm will override your configuration in the next
time
you run vdsm-tool configure.
multipath.conf should look like this:
# VDSM REVISION 1.3
# VDSM PRIVATE
defaults {
polling_interval 5
no_path_retry 12
user_friendly_names no
flush_on_last_del yes
fast_io_fail_tmo 5
dev_loss_tmo 30
max_fds 4096
}
devices {
device {
all_devs yes
no_path_retry 12
}
}
This will use 12 retries (60 seconds) timeout for any device. If you like
to
configure only your specific device, you can add a device section for
your specific server instead.
Also is there anything that we can tweak to automatically unpause the VMs
once connectivity with the arrays is re-established ?
Vdsm will resume the vms when storage monitor detect that storage became
available again.
However we cannot guarantee that storage monitoring will detect that
storage was down.
This should be improved in 4.0.
At the moment we are running a customized version of
storageServer.py, as
Ovirt has yet to include iscsi multipath support for Direct Luns out of the
box.
Would you like to share this code?
Nir
10:19 a.m.
I asked on the Dell Storage Forum and they recommend the following:
*I recommend not using a numeric value for the "no_path_retry" variable
within /etc/multipath.conf as once that numeric value is reached, if no
healthy LUNs were discovered during that defined time multipath will
disable the I/O queue altogether.*
*I do recommend, however, changing the variable value from "12" (or even
"60") to "queue" which will then allow multipathd to continue queing
I/O
until a healthy LUN is discovered (time of fail-over between controllers)
and I/O is allowed to flow once again.*
Can you see any issues with this recommendation as far as Ovirt is
concerned ?
Thanks again
*Gary Lloyd*
________________________________________________
I.T. Systems:Keele University
Finance & IT Directorate
Keele:Staffs:IC1 Building:ST5 5NB:UK
+44 1782 733063 <%2B44%201782%20733073>
________________________________________________
On 4 October 2016 at 19:11, Nir Soffer <nsoffer(a)redhat.com> wrote:
On Tue, Oct 4, 2016 at 10:51 AM, Gary Lloyd
<g.lloyd(a)keele.ac.uk> wrote:
> Hi
>
> We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct Luns for
> all our VMs.
> At the weekend during early hours an Equallogic controller failed over to
> its standby on one of our arrays and this caused about 20 of our VMs to be
> paused due to IO problems.
>
> I have also noticed that this happens during Equallogic firmware upgrades
> since we moved onto Ovirt 3.65.
>
> As recommended by Dell disk timeouts within the VMs are set to 60 seconds
> when they are hosted on an EqualLogic SAN.
>
> Is there any other timeout value that we can configure in vdsm.conf to
> stop VMs from getting paused when a controller fails over ?
>
You can set the timeout in multipath.conf.
With current multipath configuration (deployed by vdsm), when all paths to
a device
are lost (e.g. you take down all ports on the server during upgrade), all
io will fail
immediately.
If you want to allow 60 seconds gracetime in such case, you can configure:
no_path_retry 12
This will continue to monitor the paths 12 times, each 5 seconds
(assuming polling_interval=5). If some path recover during this time, the
io
can complete and the vm will not be paused.
If no path is available after these retries, io will fail and vms with
pending io
will pause.
Note that this will also cause delays in vdsm in various flows, increasing
the chance
of timeouts in engine side, or delays in storage domain monitoring.
However, the 60 seconds delay is expected only on the first time all paths
become
faulty. Once the timeout has expired, any access to the device will fail
immediately.
To configure this, you must add the # VDSM PRIVATE tag at the second line
of
multipath.conf, otherwise vdsm will override your configuration in the
next time
you run vdsm-tool configure.
multipath.conf should look like this:
# VDSM REVISION 1.3
# VDSM PRIVATE
defaults {
polling_interval 5
no_path_retry 12
user_friendly_names no
flush_on_last_del yes
fast_io_fail_tmo 5
dev_loss_tmo 30
max_fds 4096
}
devices {
device {
all_devs yes
no_path_retry 12
}
}
This will use 12 retries (60 seconds) timeout for any device. If you like
to
configure only your specific device, you can add a device section for
your specific server instead.
>
> Also is there anything that we can tweak to automatically unpause the VMs
> once connectivity with the arrays is re-established ?
>
Vdsm will resume the vms when storage monitor detect that storage became
available again.
However we cannot guarantee that storage monitoring will detect that
storage was down.
This should be improved in 4.0.
> At the moment we are running a customized version of storageServer.py, as
> Ovirt has yet to include iscsi multipath support for Direct Luns out of the
> box.
>
Would you like to share this code?
Nir
11:16 a.m.
you need the eql hit kit to make it work at least somehow better, but
hit kit requires multipathd to be disabled which is an dependency to ovirt.
so far, no real workaround seems to be known
Am 06.10.2016 um 09:19 schrieb Gary Lloyd:
I asked on the Dell Storage Forum and they recommend the following:
/I recommend not using a numeric value for the "no_path_retry" variable
within /etc/multipath.conf as once that numeric value is reached, if no
healthy LUNs were discovered during that defined time multipath will
disable the I/O queue altogether./
/I do recommend, however, changing the variable value from "12" (or even
"60") to "queue" which will then allow multipathd to continue queing
I/O
until a healthy LUN is discovered (time of fail-over between
controllers) and I/O is allowed to flow once again./
Can you see any issues with this recommendation as far as Ovirt is
concerned ?
Thanks again
/Gary Lloyd/
________________________________________________
I.T. Systems:Keele University
Finance & IT Directorate
Keele:Staffs:IC1 Building:ST5 5NB:UK
+44 1782 733063 <tel:%2B44%201782%20733073>
________________________________________________
On 4 October 2016 at 19:11, Nir Soffer <nsoffer(a)redhat.com
<mailto:nsoffer@redhat.com>> wrote:
On Tue, Oct 4, 2016 at 10:51 AM, Gary Lloyd <g.lloyd(a)keele.ac.uk
<mailto:g.lloyd@keele.ac.uk>> wrote:
Hi
We have Ovirt 3.65 with a Dell Equallogic SAN and we use Direct
Luns for all our VMs.
At the weekend during early hours an Equallogic controller
failed over to its standby on one of our arrays and this caused
about 20 of our VMs to be paused due to IO problems.
I have also noticed that this happens during Equallogic firmware
upgrades since we moved onto Ovirt 3.65.
As recommended by Dell disk timeouts within the VMs are set to
60 seconds when they are hosted on an EqualLogic SAN.
Is there any other timeout value that we can configure in
vdsm.conf to stop VMs from getting paused when a controller
fails over ?
You can set the timeout in multipath.conf.
With current multipath configuration (deployed by vdsm), when all
paths to a device
are lost (e.g. you take down all ports on the server during
upgrade), all io will fail
immediately.
If you want to allow 60 seconds gracetime in such case, you can
configure:
no_path_retry 12
This will continue to monitor the paths 12 times, each 5 seconds
(assuming polling_interval=5). If some path recover during this
time, the io
can complete and the vm will not be paused.
If no path is available after these retries, io will fail and vms
with pending io
will pause.
Note that this will also cause delays in vdsm in various flows,
increasing the chance
of timeouts in engine side, or delays in storage domain monitoring.
However, the 60 seconds delay is expected only on the first time all
paths become
faulty. Once the timeout has expired, any access to the device will
fail immediately.
To configure this, you must add the # VDSM PRIVATE tag at the second
line of
multipath.conf, otherwise vdsm will override your configuration in
the next time
you run vdsm-tool configure.
multipath.conf should look like this:
# VDSM REVISION 1.3
# VDSM PRIVATE
defaults {
polling_interval 5
no_path_retry 12
user_friendly_names no
flush_on_last_del yes
fast_io_fail_tmo 5
dev_loss_tmo 30
max_fds 4096
}
devices {
device {
all_devs yes
no_path_retry 12
}
}
This will use 12 retries (60 seconds) timeout for any device. If you
like to
configure only your specific device, you can add a device section for
your specific server instead.
Also is there anything that we can tweak to automatically
unpause the VMs once connectivity with the arrays is
re-established ?
Vdsm will resume the vms when storage monitor detect that storage
became available again.
However we cannot guarantee that storage monitoring will detect that
storage was down.
This should be improved in 4.0.
At the moment we are running a customized version of
storageServer.py, as Ovirt has yet to include iscsi multipath
support for Direct Luns out of the box.
Would you like to share this code?
Nir
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
1:07 p.m.
On Thu, Oct 6, 2016 at 10:19 AM, Gary Lloyd <g.lloyd(a)keele.ac.uk> wrote:
I asked on the Dell Storage Forum and they recommend the following:
*I recommend not using a numeric value for the "no_path_retry" variable
within /etc/multipath.conf as once that numeric value is reached, if no
healthy LUNs were discovered during that defined time multipath will
disable the I/O queue altogether.*
*I do recommend, however, changing the variable value from "12" (or even
"60") to "queue" which will then allow multipathd to continue queing
I/O
until a healthy LUN is discovered (time of fail-over between controllers)
and I/O is allowed to flow once again.*
Can you see any issues with this recommendation as far as Ovirt is
concerned ?
Yes, we cannot work with unlimited queue. This will block vdsm for unlimited
time when the next command try to access storage. Because we don't have
good isolation between different storage domains, this may cause other
storage
domains to become faulty. Also engine flows that have a timeout will fail
with
a timeout.
If you are on 3.x, this will be very painfull, on 4.0 it should be better,
but it is not
recommended.
Nir
10:37 a.m.
From the sounds of it the best we can do then is to use a 60 second
timeout
on paths in multipathd.
The main reason we use Direct Lun is because we replicate /snapshot VMs
associated Luns at SAN level as a means of disaster recovery.
I have read a bit of documentation of how to backup virtual machines in
storage domains, but the process of mounting snapshots for all our machines
within a dedicated VM doesn't seem as efficient when we have almost 300
virtual machines and only 1Gb networking.
Thanks for the advice.
*Gary Lloyd*
________________________________________________
I.T. Systems:Keele University
Finance & IT Directorate
Keele:Staffs:IC1 Building:ST5 5NB:UK
+44 1782 733063 <%2B44%201782%20733073>
________________________________________________
On 6 October 2016 at 11:07, Nir Soffer <nsoffer(a)redhat.com> wrote:
On Thu, Oct 6, 2016 at 10:19 AM, Gary Lloyd
<g.lloyd(a)keele.ac.uk> wrote:
> I asked on the Dell Storage Forum and they recommend the following:
>
> *I recommend not using a numeric value for the "no_path_retry" variable
> within /etc/multipath.conf as once that numeric value is reached, if no
> healthy LUNs were discovered during that defined time multipath will
> disable the I/O queue altogether.*
>
> *I do recommend, however, changing the variable value from "12" (or even
> "60") to "queue" which will then allow multipathd to continue
queing I/O
> until a healthy LUN is discovered (time of fail-over between controllers)
> and I/O is allowed to flow once again.*
>
> Can you see any issues with this recommendation as far as Ovirt is
> concerned ?
>
Yes, we cannot work with unlimited queue. This will block vdsm for
unlimited
time when the next command try to access storage. Because we don't have
good isolation between different storage domains, this may cause other
storage
domains to become faulty. Also engine flows that have a timeout will fail
with
a timeout.
If you are on 3.x, this will be very painfull, on 4.0 it should be better,
but it is not
recommended.
Nir
2968
days inactive
2971
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7 comments
4 participants
participants (4)
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Gary Lloyd -
InterNetX - Juergen Gotteswinter -
Michal Skrivanek -
Nir Soffer