On Wed, Jul 13, 2016 at 10:58 AM, Dmitry Melekhov <[email protected]> wrote:
> 13.07.2016 09:26, Pranith Kumar Karampuri пишет: > > > > On Wed, Jul 13, 2016 at 10:50 AM, Dmitry Melekhov < <[email protected]> > [email protected]> wrote: > >> 13.07.2016 09:16, Pranith Kumar Karampuri пишет: >> >> >> >> On Wed, Jul 13, 2016 at 10:38 AM, Dmitry Melekhov <[email protected]> wrote: >> >>> 13.07.2016 09:04, Pranith Kumar Karampuri пишет: >>> >>> >>> >>> On Wed, Jul 13, 2016 at 10:29 AM, Dmitry Melekhov < <[email protected]> >>> [email protected]> wrote: >>> >>>> 13.07.2016 08:56, Pranith Kumar Karampuri пишет: >>>> >>>> >>>> >>>> On Wed, Jul 13, 2016 at 10:23 AM, Dmitry Melekhov < <[email protected]> >>>> [email protected]> wrote: >>>> >>>>> 13.07.2016 08:46, Pranith Kumar Karampuri пишет: >>>>> >>>>> >>>>> >>>>> On Wed, Jul 13, 2016 at 10:10 AM, Dmitry Melekhov < <[email protected]> >>>>> [email protected]> wrote: >>>>> >>>>>> 13.07.2016 08:36, Pranith Kumar Karampuri пишет: >>>>>> >>>>>> >>>>>> >>>>>> On Wed, Jul 13, 2016 at 9:35 AM, Dmitry Melekhov < <[email protected]> >>>>>> [email protected]> wrote: >>>>>> >>>>>>> 13.07.2016 01:52, Anuradha Talur пишет: >>>>>>> >>>>>>>> >>>>>>>> ----- Original Message ----- >>>>>>>> >>>>>>>>> From: "Dmitry Melekhov" < <[email protected]>[email protected]> >>>>>>>>> To: "Pranith Kumar Karampuri" < <[email protected]> >>>>>>>>> [email protected]> >>>>>>>>> Cc: "gluster-users" < <[email protected]> >>>>>>>>> [email protected]> >>>>>>>>> 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. >>> >>> So only supported platfrom is linux? Or, may be, it is better to improve >>> self-healing to detect missing or wrong length files, I guess this is very >>> low cost in terms of host resources operation. >>> Just a suggestion, may be we need to look to alternatives in near >>> future.... >>> >>> This is a corner case, from design perspective it is generally not a >> good idea to optimize for the corner case. It is better to protect >> ourselves from the corner case (SElinux etc) or you can also use snapshots >> to protect against these kind of mishaps. >> >> Sorry, I'm not agree. >> As you know if on access missed or wrong lenghted file from fuse client >> it is restored (healed), i.e. gluster recognizes file is wrong and heal it >> , so I do not see any reason to provide this such function as self-healing. >> Thank you! >> >> Ah! Now how do you suggest we keep track of which of 10s of millions of > files the user accidentally deleted from the brick without gluster's > knowledge? Once it comes to gluster's knowledge we can do something. But > how does gluster become aware of something it is not keeping track of? At > the time you access it gluster knows something went wrong so it restores > it. If you change something on the bricks even by accident all the data > gluster keeps (similar to journal) is a waste. Even the disk filesystems > will ask you to do fsck if something unexpected happens so full self-heal > is similar operation. > > > You are absolutely right- question is why gluster does not become aware > about such problem is case of self-healing? > Because the operations that are performed directly on brick do not go through gluster stack. > > > > -- > Pranith > > > -- Pranith
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