[Ocfs2-devel] OCFS2 causing system instability

[Joseph Qi]

Hi Gang,

On 2016/1/21 10:23, Gang He wrote:
> Hi Guy,
> 
> 
> 
> 
>>>>
>> Hello Gang,
>>
>> Thank you for the quick response, it looks like the right direction for me
>> - similar to other file systems (not clustered) have.
>>
>> I've checked and saw that the mount forwards this parameter to the OCFS2
>> kernel driver and it looks the version I have in my kernel does not support
>> the errors=continue but only panic and remount-ro.
>>
>> You've mentioned the "latest code" ... my question is:  On which kernel
>> version it should be supported? I'm currently using 3.16 on ubuntu 14.04.
> 
> please refer to git commit in kernel.git
> commit 7d0fb9148ab6f52006de7cce18860227594ba872
> Author: Goldwyn Rodrigues <rgoldwyn at suse.de>
> Date:   Fri Sep 4 15:44:11 2015 -0700
> 
>     ocfs2: add errors=continue
> 
>     OCFS2 is often used in high-availaibility systems.  However, ocfs2
>     converts the filesystem to read-only at the drop of the hat.  This may
>     not be necessary, since turning the filesystem read-only would affect
>     other running processes as well, decreasing availability.
> 
> Finally, as Joseph said, you can't unplug a hard disk on a running file system, this is a shared disk cluster file system, not a multiple copy distributed file system.
Unlike ceph, OCFS2 depends on SAN to configure redundant data check,
for example, RAID5 and hotspare disk.
If deployed on local disk and used in local mode, there will be no
heartbeat and it behaviors like ext3.

Thanks,
Joseph

> option "errors=continue" can let the file system continue when encountering a local inode meta-data corruption problem.
> 
> Thanks
> Gang 
> 
>>
>>
>> Thanks,
>>
>> Guy
>>
>> On Wed, Jan 20, 2016 at 4:21 AM, Gang He <ghe at suse.com> wrote:
>>
>>> Hello guy,
>>>
>>> First, OCFS2 is a shared disk cluster file system, not a distibuted file
>>> system (like Ceph), we only share the same data/metadata copy on this
>>> shared disk, please make sure this shared disk are always integrated.
>>> Second, if file system encounters any error, the behavior is specified by
>>> mount options "errors=xxx",
>>> The latest code should support "errors=continue" option, that means file
>>> system will not panic the OS, and just return -EIO error and let the file
>>> system continue.
>>>
>>> Thanks
>>> Gang
>>>
>>>
>>>>>>
>>>> Dear OCFS2 guys,
>>>>
>>>>
>>>>
>>>> My name is Guy, and I'm testing ocfs2 due to its features as a clustered
>>>> filesystem that I need.
>>>>
>>>> As part of the stability and reliability test I’ve performed, I've
>>>> encountered an issue with ocfs2 (format + mount + remove disk...), that I
>>>> wanted to make sure it is a real issue and not just a mis-configuration.
>>>>
>>>>
>>>>
>>>> The main concern is that the stability of the whole system is compromised
>>>> when a single disk/volumes fails. It looks like the OCFS2 is not handling
>>>> the error correctly but stuck in an endless loop that interferes with the
>>>> work of the server.
>>>>
>>>>
>>>>
>>>> I’ve test tested two cluster configurations – (1) Corosync/Pacemaker and
>>>> (2) o2cb that react similarly.
>>>>
>>>> Following the process and log entries:
>>>>
>>>>
>>>> Also below additional configuration that were tested.
>>>>
>>>>
>>>> Node 1:
>>>>
>>>> =======
>>>>
>>>> 1. service corosync start
>>>>
>>>> 2. service dlm start
>>>>
>>>> 3. mkfs.ocfs2 -v -Jblock64 -b 4096 --fs-feature-level=max-features
>>>> --cluster-=pcmk --cluster-name=cluster-name -N 2 /dev/<path to device>
>>>>
>>>> 4. mount -o
>>>> rw,noatime,nodiratime,data=writeback,heartbeat=none,cluster_stack=pcmk
>>>> /dev/<path to device> /mnt/ocfs2-mountpoint
>>>>
>>>>
>>>>
>>>> Node 2:
>>>>
>>>> =======
>>>>
>>>> 5. service corosync start
>>>>
>>>> 6. service dlm start
>>>>
>>>> 7. mount -o
>>>> rw,noatime,nodiratime,data=writeback,heartbeat=none,cluster_stack=pcmk
>>>> /dev/<path to device> /mnt/ocfs2-mountpoint
>>>>
>>>>
>>>>
>>>> So far all is working well, including reading and writing.
>>>>
>>>> Next
>>>>
>>>> 8. I’ve physically, pull out the disk at /dev/<path to device> to
>>> simulate
>>>> a hardware failure (that may occur…) , in real life the disk is (hardware
>>>> or software) protected. Nonetheless, I’m testing a hardware failure that
>>>> the one of the OCFS2 file systems in my server fails.
>>>>
>>>> Following  - messages observed in the system log (see below) and
>>>>
>>>> ==>  9. kernel panic(!) ... in one of the nodes or on both, or reboot on
>>>> one of the nodes or both.
>>>>
>>>>
>>>> Is there any configuration or set of parameters that will enable the
>>> system
>>>> to continue working, disabling the access to the failed disk without
>>>> compromising the system stability and not cause the kernel to panic?!
>>>>
>>>>
>>>>
>>>> >From my point of view it looks basics – when a hardware failure occurs:
>>>>
>>>> 1. All remaining hardware should continue working
>>>>
>>>> 2. The failed disk/volume should be inaccessible – but not compromise the
>>>> whole system availability (Kernel panic).
>>>>
>>>> 3. OCFS2 “understands” there’s a failed disk and stop trying to access
>>> it.
>>>>
>>>> 3. All disk commands such as mount/umount, df etc. should continue
>>> working.
>>>>
>>>> 4. When a new/replacement drive is connected to the system, it can be
>>>> accessed.
>>>>
>>>> My settings:
>>>>
>>>> ubuntu 14.04
>>>>
>>>> linux:  3.16.0-46-generic
>>>>
>>>> mkfs.ocfs2 1.8.4 (downloaded from git)
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Some other scenarios which also were tested:
>>>>
>>>> 1. Remove the max-features in the mkfs (i.e. mkfs.ocfs2 -v -Jblock64 -b
>>>> 4096 --cluster-stack=pcmk --cluster-name=cluster-name -N 2 /dev/<path to
>>>> device>)
>>>>
>>>> This improved in some of the cases with no kernel panic but still the
>>>> stability of the system was compromised, the syslog indicates that
>>>> something unrecoverable is going on (See below - Appendix A1).
>>> Furthermore,
>>>> System is hanging when trying to software reboot.
>>>>
>>>> 2. Also tried with the o2cb stack, with similar outcomes.
>>>>
>>>> 3. The configuration was also tested with (1,2 and
> 
> 
> 
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