On Wed, Jul 13, 2016 at 11:27 AM, Dmitry Melekhov <[email protected]> wrote:
> 13.07.2016 09:50, Pranith Kumar Karampuri пишет: > > > > On Wed, Jul 13, 2016 at 11:11 AM, Dmitry Melekhov < <[email protected]> > [email protected]> wrote: > >> 13.07.2016 09:36, Pranith Kumar Karampuri пишет: >> >> >> >> 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]> >>>> [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. >> >> >> >> OK, I'll repeat- >> 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. >> > > For which you need accessing the file. > > That's right. > > For which you need full crawl. You can't detect the modification which > doesn't go through the stack so this is the only possibility. > > > OK, then, if self-heal is really useless and no possible way to get it > will be provided, I guess we'll use external script to check bricks > directories consistency, > don't think ls and diff will get much resources. > How is this different from full self-heal? > > Thank you! > > p.s. > still can't understand why it can't be implemented in gluster... :-( > > >> >>> >>> >>> -- >>> Pranith >>> >>> >>> >> >> >> -- >> Pranith >> >> >> > > > -- > Pranith > > > -- Pranith
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