On Wed, Jul 13, 2016 at 11:11 AM, Dmitry Melekhov <[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]> > [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]> 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. 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. > > >> >> >> -- >> Pranith >> >> >> > > > -- > Pranith > > > -- Pranith
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