[Gluster-users] 3.7.13, index healing broken?

[Pranith Kumar Karampuri]

On Wed, Jul 13, 2016 at 10:29 AM, Dmitry Melekhov <dm at belkam.com> wrote:

> 13.07.2016 08:56, Pranith Kumar Karampuri пишет:
>
>
>
> On Wed, Jul 13, 2016 at 10:23 AM, Dmitry Melekhov < <dm at belkam.com>
> dm at belkam.com> wrote:
>
>> 13.07.2016 08:46, Pranith Kumar Karampuri пишет:
>>
>>
>>
>> On Wed, Jul 13, 2016 at 10:10 AM, Dmitry Melekhov < <dm at belkam.com>
>> dm at belkam.com> wrote:
>>
>>> 13.07.2016 08:36, Pranith Kumar Karampuri пишет:
>>>
>>>
>>>
>>> On Wed, Jul 13, 2016 at 9:35 AM, Dmitry Melekhov < <dm at belkam.com>
>>> dm at belkam.com> wrote:
>>>
>>>> 13.07.2016 01:52, Anuradha Talur пишет:
>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>>
>>>>>> From: "Dmitry Melekhov" < <dm at belkam.com>dm at belkam.com>
>>>>>> To: "Pranith Kumar Karampuri" < <pkarampu at redhat.com>
>>>>>> pkarampu at redhat.com>
>>>>>> Cc: "gluster-users" < <gluster-users at gluster.org>
>>>>>> gluster-users at gluster.org>
>>>>>> Sent: Tuesday, July 12, 2016 9:27:17 PM
>>>>>> Subject: Re: [Gluster-users] 3.7.13, index healing broken?
>>>>>>
>>>>>>
>>>>>>
>>>>>> 12.07.2016 17:39, Pranith Kumar Karampuri пишет:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Wow, what are the steps to recreate the problem?
>>>>>>
>>>>>> just set file length to zero, always reproducible.
>>>>>>
>>>>>> If you are setting the file length to 0 on one of the bricks (looks
>>>>> like
>>>>> that is the case), it is not a bug.
>>>>>
>>>>> Index heal relies on failures seen from the mount point(s)
>>>>> to identify the files that need heal. It won't be able to recognize
>>>>> any file
>>>>> modification done directly on bricks. Same goes for heal info command
>>>>> which
>>>>> is the reason heal info also shows 0 entries.
>>>>>
>>>>
>>>> Well, this makes self-heal useless then- if any file is accidently
>>>> corrupted or deleted (yes! if file is deleted directly from brick this is
>>>> no recognized by idex heal too), then it will not be self-healed, because
>>>> self-heal uses index heal.
>>>>
>>>
>>> It is better to look into bit-rot feature if you want to guard against
>>> these kinds of problems.
>>>
>>>
>>> Bit rot detects bit problems, not missing files or their wrong length,
>>> i.e. this is overhead for such simple task.
>>>
>>
>> It detects wrong length. Because checksum won't match anymore.
>>
>>
>> Yes, sure. I guess that it will detect missed files too. But it needs far
>> more resources, then just comparing directories in bricks?
>>
>>
>> What use-case you are trying out is leading to changing things directly
>> on the brick?
>>
>> I'm trying to test gluster failure tolerance and right now I'm not happy
>> with it...
>>
>
> Which cases of fault tolerance are you not happy with? Making changes
> directly on the brick or anything else as well?
>
> I'll repeat:
> As I already said- if I for some reason ( real case  can be only by
> accident ) will delete file this will not be detected by self-heal daemon,
> and, thus, will lead to lower replication level, i.e. lower failure
> tolerance.
>

To prevent such accidents you need to set selinux policies so that files
under the brick are not modified by accident by any user. At least that is
the solution I remember when this was discussed 3-4 years back.

-- 
Pranith
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