Bug 1225162

Nir, looking at the gerrit patch and the ml thread, it looks like this is something which can be fixed in vdsm, right?

(In reply to Fabian Deutsch from comment #1)
> Nir, looking at the gerrit patch and the ml thread, it looks like this is
> something which can be fixed in vdsm, right?

It think that the multipath configuration that vdsm uses is wrong, missing some
settings for this storage server. However the settings I recommended, taken from
multipath.conf.defaults, and modified for vdsm, did not eliminate the problem.

So yes, vdsm need to ship better configuration for this server, but so multipath
builtin setup is probably also need to be fixed.

I posted https://gerrit.ovirt.org/41244, but we cannot ship this without testing
with this storage server, or getting ack from the storage vendor.

Chris,

Did you check with the vendor about the storage server configuration?

Can you upload some logs so we can investigate this further?

We need:
/var/log/messages
/var/log/vdsm/vdsm/vdsm.log
engine.log

Just got this figured out yesterday. The underlying issue was a bad disk on the Compellent's tier 2 storage. This disk was causing read latency issues. The default multipath.conf and iscsi.conf was causing it to fail when combined with the high latency.

So the good news is that the updated configs made oVirt more resilient. The bad news is that the Compellent reports the disk as "healthy" despite it having been logging this latency this the entire time.

With the inclusion for the updated configs in future oVirt versions, this can be marked as solved. Thank you again for all the help.

(In reply to Chris Jones from comment #4)
> Just got this figured out yesterday. The underlying issue was a bad disk on
> the Compellent's tier 2 storage. This disk was causing read latency issues.
> The default multipath.conf and iscsi.conf was causing it to fail when
> combined with the high latency.
> 
> So the good news is that the updated configs made oVirt more resilient. The
> bad news is that the Compellent reports the disk as "healthy" despite it
> having been logging this latency this the entire time.
> 
> With the inclusion for the updated configs in future oVirt versions, this
> can be marked as solved. Thank you again for all the help.

Forgot to mention. We have no more storage domain errors in the logs now that the bad disk was removed.

Lowering severity and priority as the root cause was the storage server.

Keeping this open since we need to improve the related multipath
configuration.

Patch was abandoned, moving back to NEW

Fixed by removing the incorrect configuration for COMPELNT/Compellent Vol
exposing the builtin configuration for this device.

Vdsm overrides now only the "no_path_retry" option, using "fail". This 
value is required by vdsm to prevent long delays in storage related 
threads, blocked on lvm or multiapth operations, because io to one device
is queued.

Nir, is there anything worth while documenting here?

(In reply to Allon Mureinik from comment #9)
> Nir, is there anything worth while documenting here?

See comment 8. Not sure that adding doc text (we had bad configuration, fixed) has any value.

(In reply to Nir Soffer from comment #10)
> (In reply to Allon Mureinik from comment #9)
> > Nir, is there anything worth while documenting here?
> 
> See comment 8. Not sure that adding doc text (we had bad configuration,
> fixed) has any value.
IMHO, there isn't, thanks for the clarification.
Setting requires-doctext-

'devices' section in multipath.conf has 'all_devs=yes' and 'no_path_retry=fail'


devices {                                                                                                                                                                                                            
    device {                                                                                                                                                                                                                                                                                                                  
        all_devs                yes                                                                                                                                                                                  
        no_path_retry           fail
    }
}


Nir, can I move to VERIFIED based on that?

(In reply to Elad from comment #12)
> 'devices' section in multipath.conf has 'all_devs=yes' and
> 'no_path_retry=fail'
> 
> 
> devices {                                                                   
> 
>     device {                                                                
> 
>         all_devs                yes                                         
> 
>         no_path_retry           fail
>     }
> }
> 
> 
> Nir, can I move to VERIFIED based on that?

No, you should check the effect of this configuration.

The best way is to check the actual storage, but we cannot do that,
unless you find a way to make your server looks like this product.

What you can do is to check the effective settings for this device,
using multipath:

$ multipathd show config | less

Now locate the device by the vendor/product - in this case it is
the vendor name - "COMPELNT":

        device {
                vendor "COMPELNT"
                product "Compellent Vol"
                path_grouping_policy "multibus"
                path_checker "tur"
                features "0"
                hardware_handler "0"
                prio "const"
                failback immediate
                rr_weight "uniform"
                no_path_retry "fail"
        }

Check:

    features "0"
    no_path_retry "fail"

Compare these settings with ovirt-3.5.

On latest vdsm (vdsm-4.17.10.1-0.el7ev.noarch), under dell vendor - "COMPELNT", The following is configured:

        device {
                vendor "COMPELNT"
                product "Compellent Vol"
                path_grouping_policy "multibus"
                path_checker "tur"
                features "0"
                hardware_handler "0"
                prio "const"
                failback immediate
                rr_weight "uniform"
                no_path_retry "fail"
        }



(features "0"   no_path_retry "fail")


On 3.5 (vdsm-4.16.29-1.el7ev.x86_64), it's configured as follows:


        device {
                vendor "COMPELNT"
                product "Compellent Vol"
                path_grouping_policy "multibus"
                path_checker "tur"
                features "0"
                hardware_handler "0"
                prio "const"
                failback immediate
                rr_weight "uniform"
                no_path_retry "fail"
        }




(features "0"   no_path_retry "fail")



Nir, it looks the same on both.

(In reply to Elad from comment #14)
> Nir, it looks the same on both.

Can you post the multiapth.conf on the 3.5 setup?

In 3.5, I expect to find this multipath configuration:

    device {
        vendor                  "COMPELNT"
        product                 "Compellent Vol"
        no_path_retry           fail
    }

Which is incorrect because it overrides all the settings other then
no_path_retry to the defualts.

It is possible that on the system you tested, multipath defualts
are the same for this device, which can explain why the effective
setting are the same.

Anyway, our configuration works as expected, so I thinks we are
done with this.

On 3.5 - 7.1 it is as I pasted on comment #14. 

On the other hand, on 3.5 - 6.7, it's as follows:


device {
                vendor "COMPELNT"
                product "Compellent Vol"
                path_grouping_policy multibus
                getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
                path_selector "round-robin 0"
                path_checker tur
                features "0"
                hardware_handler "0"
                prio const
                failback immediate
                rr_weight uniform
                no_path_retry fail
                rr_min_io 1000
                rr_min_io_rq 1
        }



multipath.conf from the 3.5 - 7.1 host:


[root@camel-vdsb ~]# cat /etc/multipath.conf 
# RHEV REVISION 1.1

defaults {
    polling_interval        5
    getuid_callout          "/usr/lib/udev/scsi_id --whitelisted --replace-whitespace --device=/dev/%n"
    no_path_retry           fail
    user_friendly_names     no
    flush_on_last_del       yes
    fast_io_fail_tmo        5
    dev_loss_tmo            30
    max_fds                 4096
}

devices {
device {
    vendor                  "HITACHI"
    product                 "DF.*"
    getuid_callout          "/usr/lib/udev/scsi_id --whitelisted --replace-whitespace --device=/dev/%n"
}
device {
    vendor                  "COMPELNT"
    product                 "Compellent Vol"
    no_path_retry           fail
}
device {
    # multipath.conf.default
    vendor                  "DGC"
    product                 ".*"
    product_blacklist       "LUNZ"
    path_grouping_policy    "group_by_prio"
    path_checker            "emc_clariion"
    hardware_handler        "1 emc"
    prio                    "emc"
    failback                immediate
    rr_weight               "uniform"
    # vdsm required configuration
    getuid_callout          "/usr/lib/udev/scsi_id --whitelisted --replace-whitespace --device=/dev/%n"
    features                "0"
    no_path_retry           fail
}

(In reply to Elad from comment #16)
The effective configuration on the 7 is strange, I would expect
the same values as seen on 6.7.

I will check this with multiapth maintainer - maybe there were changes
in multipath defaults, or some patch is missing in multipath on 7.

Hi Nir, 

Did you get an answer?

(In reply to Elad from comment #18)
This seems to be a difference in the way rhel 6.7 and 7.2 are configured.

When this bug was reported, the the behavior with the following configuration:

device {
    vendor                  "COMPELNT"
    product                 "Compellent Vol"
    no_path_retry           fail
}

Was different from the current configuration:

device {
         all_devs                yes                                                                                                                                      
         no_path_retry           fail
}

But now they are seems to be the same for this device.

Anyway, on our side, the new configuration supports all devices,
and behave as expected.

This can be safely closed.

Moving to VERIFIED Based on comment #19

oVirt 3.6.0 has been released, closing current release