[Gluster-users] disperse volume file to subvolume mapping
Serkan Çoban
cobanserkan at gmail.com
Thu Apr 21 12:23:00 UTC 2016
>Has the rebalance operation finished successfully ? has it skipped any files ?
Yes according to gluster v rebalance status it is completed without any errors.
rebalance status report is like:
Node Rebalanced files size Scanned
failures skipped
1.1.1.185 158 29GB 1720
0 314
1.1.1.205 93 46.5GB 761
0 95
1.1.1.225 74 37GB 779
0 94
All other hosts has 0 values.
I double check that files with '---------T' attributes are there,
maybe some of them deleted but I still see them in bricks...
I am also concerned why part files not distributed to all 60 nodes?
Rebalance should do that?
On Thu, Apr 21, 2016 at 1:55 PM, Xavier Hernandez <xhernandez at datalab.es> wrote:
> Hi Serkan,
>
> On 21/04/16 12:39, Serkan Çoban wrote:
>>
>> I started a gluster v rebalance v0 start command hoping that it will
>> equally redistribute files across 60 nodes but it did not do that...
>> why it did not redistribute files? any thoughts?
>
>
> Has the rebalance operation finished successfully ? has it skipped any files
> ?
>
> After a successful rebalance all files with attributes '---------T' should
> have disappeared.
>
>
>>
>> On Thu, Apr 21, 2016 at 11:24 AM, Xavier Hernandez
>> <xhernandez at datalab.es> wrote:
>>>
>>> Hi Serkan,
>>>
>>> On 21/04/16 10:07, Serkan Çoban wrote:
>>>>>
>>>>>
>>>>> I think the problem is in the temporary name that distcp gives to the
>>>>> file while it's being copied before renaming it to the real name. Do
>>>>> you
>>>>> know what is the structure of this name ?
>>>>
>>>>
>>>> Distcp temporary file name format is:
>>>> ".distcp.tmp.attempt_1460381790773_0248_m_000001_0" and the same
>>>> temporary file name used by one map process. For example I see in the
>>>> logs that one map copies files part-m-00031,part-m-00047,part-m-00063
>>>> sequentially and they all use same temporary file name above. So no
>>>> original file name appears in temporary file name.
>>>
>>>
>>>
>>> This explains the problem. With the default options, DHT sends all files
>>> to
>>> the subvolume that should store a file named 'distcp.tmp'.
>>>
>>> With this temporary name format, little can be done.
>>>
>>>>
>>>> I will check if we can modify distcp behaviour, or we have to write
>>>> our mapreduce procedures instead of using distcp.
>>>>
>>>>> 2. define the option 'extra-hash-regex' to an expression that matches
>>>>> your temporary file names and returns the same name that will finally
>>>>> have.
>>>>> Depending on the differences between original and temporary file names,
>>>>> this
>>>>> option could be useless.
>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the
>>>>> name conversion, so the files will be evenly distributed. However this
>>>>> will
>>>>> cause a lot of files placed in incorrect subvolumes, creating a lot of
>>>>> link
>>>>> files until a rebalance is executed.
>>>>
>>>>
>>>>
>>>> How can I set these options?
>>>
>>>
>>>
>>> You can set gluster options using:
>>>
>>> gluster volume set <volname> <option> <value>
>>>
>>> for example:
>>>
>>> gluster volume set v0 rsync-hash-regex none
>>>
>>> Xavi
>>>
>>>
>>>>
>>>>
>>>>
>>>> On Thu, Apr 21, 2016 at 10:00 AM, Xavier Hernandez
>>>> <xhernandez at datalab.es> wrote:
>>>>>
>>>>>
>>>>> Hi Serkan,
>>>>>
>>>>> I think the problem is in the temporary name that distcp gives to the
>>>>> file
>>>>> while it's being copied before renaming it to the real name. Do you
>>>>> know
>>>>> what is the structure of this name ?
>>>>>
>>>>> DHT selects the subvolume (in this case the ec set) on which the file
>>>>> will
>>>>> be stored based on the name of the file. This has a problem when a file
>>>>> is
>>>>> being renamed, because this could change the subvolume where the file
>>>>> should
>>>>> be found.
>>>>>
>>>>> DHT has a feature to avoid incorrect file placements when executing
>>>>> renames
>>>>> for the rsync case. What it does is to check if the file matches the
>>>>> following regular expression:
>>>>>
>>>>> ^\.(.+)\.[^.]+$
>>>>>
>>>>> If a match is found, it only considers the part between parenthesis to
>>>>> calculate the destination subvolume.
>>>>>
>>>>> This is useful for rsync because temporary file names are constructed
>>>>> in
>>>>> the
>>>>> following way: suppose the original filename is 'test'. The temporary
>>>>> filename while rsync is being executed is made by prepending a dot and
>>>>> appending '.<random chars>': .test.712hd
>>>>>
>>>>> As you can see, the original name and the part of the name between
>>>>> parenthesis that matches the regular expression are the same. This
>>>>> causes
>>>>> that, after renaming the temporary file to its original filename, both
>>>>> files
>>>>> will be considered to belong to the same subvolume by DHT.
>>>>>
>>>>> In your case it's very probable that distcp uses a temporary name like
>>>>> '.part.<number>'. In this case the portion of the name used to select
>>>>> the
>>>>> subvolume is always 'part'. This would explain why all files go to the
>>>>> same
>>>>> subvolume. Once the file is renamed to another name, DHT realizes that
>>>>> it
>>>>> should go to another subvolume. At this point it creates a link file
>>>>> (those
>>>>> files with access rights = '---------T') in the correct subvolume but
>>>>> it
>>>>> doesn't move it. As you can see, this kind of files are better
>>>>> balanced.
>>>>>
>>>>> To solve this problem you have three options:
>>>>>
>>>>> 1. change the temporary filename used by distcp to correctly match the
>>>>> regular expression. I'm not sure if this can be configured, but if this
>>>>> is
>>>>> possible, this is the best option.
>>>>>
>>>>> 2. define the option 'extra-hash-regex' to an expression that matches
>>>>> your
>>>>> temporary file names and returns the same name that will finally have.
>>>>> Depending on the differences between original and temporary file names,
>>>>> this
>>>>> option could be useless.
>>>>>
>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the
>>>>> name
>>>>> conversion, so the files will be evenly distributed. However this will
>>>>> cause
>>>>> a lot of files placed in incorrect subvolumes, creating a lot of link
>>>>> files
>>>>> until a rebalance is executed.
>>>>>
>>>>> Xavi
>>>>>
>>>>>
>>>>> On 20/04/16 14:13, Serkan Çoban wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Here is the steps that I do in detail and relevant output from bricks:
>>>>>>
>>>>>> I am using below command for volume creation:
>>>>>> gluster volume create v0 disperse 20 redundancy 4 \
>>>>>> 1.1.1.{185..204}:/bricks/02 \
>>>>>> 1.1.1.{205..224}:/bricks/02 \
>>>>>> 1.1.1.{225..244}:/bricks/02 \
>>>>>> 1.1.1.{185..204}:/bricks/03 \
>>>>>> 1.1.1.{205..224}:/bricks/03 \
>>>>>> 1.1.1.{225..244}:/bricks/03 \
>>>>>> 1.1.1.{185..204}:/bricks/04 \
>>>>>> 1.1.1.{205..224}:/bricks/04 \
>>>>>> 1.1.1.{225..244}:/bricks/04 \
>>>>>> 1.1.1.{185..204}:/bricks/05 \
>>>>>> 1.1.1.{205..224}:/bricks/05 \
>>>>>> 1.1.1.{225..244}:/bricks/05 \
>>>>>> 1.1.1.{185..204}:/bricks/06 \
>>>>>> 1.1.1.{205..224}:/bricks/06 \
>>>>>> 1.1.1.{225..244}:/bricks/06 \
>>>>>> 1.1.1.{185..204}:/bricks/07 \
>>>>>> 1.1.1.{205..224}:/bricks/07 \
>>>>>> 1.1.1.{225..244}:/bricks/07 \
>>>>>> 1.1.1.{185..204}:/bricks/08 \
>>>>>> 1.1.1.{205..224}:/bricks/08 \
>>>>>> 1.1.1.{225..244}:/bricks/08 \
>>>>>> 1.1.1.{185..204}:/bricks/09 \
>>>>>> 1.1.1.{205..224}:/bricks/09 \
>>>>>> 1.1.1.{225..244}:/bricks/09 \
>>>>>> 1.1.1.{185..204}:/bricks/10 \
>>>>>> 1.1.1.{205..224}:/bricks/10 \
>>>>>> 1.1.1.{225..244}:/bricks/10 \
>>>>>> 1.1.1.{185..204}:/bricks/11 \
>>>>>> 1.1.1.{205..224}:/bricks/11 \
>>>>>> 1.1.1.{225..244}:/bricks/11 \
>>>>>> 1.1.1.{185..204}:/bricks/12 \
>>>>>> 1.1.1.{205..224}:/bricks/12 \
>>>>>> 1.1.1.{225..244}:/bricks/12 \
>>>>>> 1.1.1.{185..204}:/bricks/13 \
>>>>>> 1.1.1.{205..224}:/bricks/13 \
>>>>>> 1.1.1.{225..244}:/bricks/13 \
>>>>>> 1.1.1.{185..204}:/bricks/14 \
>>>>>> 1.1.1.{205..224}:/bricks/14 \
>>>>>> 1.1.1.{225..244}:/bricks/14 \
>>>>>> 1.1.1.{185..204}:/bricks/15 \
>>>>>> 1.1.1.{205..224}:/bricks/15 \
>>>>>> 1.1.1.{225..244}:/bricks/15 \
>>>>>> 1.1.1.{185..204}:/bricks/16 \
>>>>>> 1.1.1.{205..224}:/bricks/16 \
>>>>>> 1.1.1.{225..244}:/bricks/16 \
>>>>>> 1.1.1.{185..204}:/bricks/17 \
>>>>>> 1.1.1.{205..224}:/bricks/17 \
>>>>>> 1.1.1.{225..244}:/bricks/17 \
>>>>>> 1.1.1.{185..204}:/bricks/18 \
>>>>>> 1.1.1.{205..224}:/bricks/18 \
>>>>>> 1.1.1.{225..244}:/bricks/18 \
>>>>>> 1.1.1.{185..204}:/bricks/19 \
>>>>>> 1.1.1.{205..224}:/bricks/19 \
>>>>>> 1.1.1.{225..244}:/bricks/19 \
>>>>>> 1.1.1.{185..204}:/bricks/20 \
>>>>>> 1.1.1.{205..224}:/bricks/20 \
>>>>>> 1.1.1.{225..244}:/bricks/20 \
>>>>>> 1.1.1.{185..204}:/bricks/21 \
>>>>>> 1.1.1.{205..224}:/bricks/21 \
>>>>>> 1.1.1.{225..244}:/bricks/21 \
>>>>>> 1.1.1.{185..204}:/bricks/22 \
>>>>>> 1.1.1.{205..224}:/bricks/22 \
>>>>>> 1.1.1.{225..244}:/bricks/22 \
>>>>>> 1.1.1.{185..204}:/bricks/23 \
>>>>>> 1.1.1.{205..224}:/bricks/23 \
>>>>>> 1.1.1.{225..244}:/bricks/23 \
>>>>>> 1.1.1.{185..204}:/bricks/24 \
>>>>>> 1.1.1.{205..224}:/bricks/24 \
>>>>>> 1.1.1.{225..244}:/bricks/24 \
>>>>>> 1.1.1.{185..204}:/bricks/25 \
>>>>>> 1.1.1.{205..224}:/bricks/25 \
>>>>>> 1.1.1.{225..244}:/bricks/25 \
>>>>>> 1.1.1.{185..204}:/bricks/26 \
>>>>>> 1.1.1.{205..224}:/bricks/26 \
>>>>>> 1.1.1.{225..244}:/bricks/26 \
>>>>>> 1.1.1.{185..204}:/bricks/27 \
>>>>>> 1.1.1.{205..224}:/bricks/27 \
>>>>>> 1.1.1.{225..244}:/bricks/27 force
>>>>>>
>>>>>> then I mount volume on 50 clients:
>>>>>> mount -t glusterfs 1.1.1.185:/v0 /mnt/gluster
>>>>>>
>>>>>> then I make a directory from one of the clients and chmod it.
>>>>>> mkdir /mnt/gluster/s1 && chmod 777 /mnt/gluster/s1
>>>>>>
>>>>>> then I start distcp on clients, there are 1059X8.8GB files in one
>>>>>> folder
>>>>>> and
>>>>>> they will be copied to /mnt/gluster/s1 with 100 parallel which means 2
>>>>>> copy jobs per client at same time.
>>>>>> hadoop distcp -m 100 http://nn1:8020/path/to/teragen-10tb
>>>>>> file:///mnt/gluster/s1
>>>>>>
>>>>>> After job finished here is the status of s1 directory from bricks:
>>>>>> s1 directory is present in all 1560 brick.
>>>>>> s1/teragen-10tb folder is present in all 1560 brick.
>>>>>>
>>>>>> full listing of files in bricks:
>>>>>> https://www.dropbox.com/s/rbgdxmrtwz8oya8/teragen_list.zip?dl=0
>>>>>>
>>>>>> You can ignore the .crc files in the brick output above, they are
>>>>>> checksum files...
>>>>>>
>>>>>> As you can see part-m-xxxx files written only some bricks in nodes
>>>>>> 0205..0224
>>>>>> All bricks have some files but they have zero size.
>>>>>>
>>>>>> I increase file descriptors to 65k so it is not the issue...
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, Apr 20, 2016 at 9:34 AM, Xavier Hernandez
>>>>>> <xhernandez at datalab.es>
>>>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hi Serkan,
>>>>>>>
>>>>>>> On 19/04/16 15:16, Serkan Çoban wrote:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> I assume that gluster is used to store the intermediate files
>>>>>>>>>>> before
>>>>>>>>>>> the reduce phase
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Nope, gluster is the destination for distcp command. hadoop distcp
>>>>>>>> -m
>>>>>>>> 50 http://nn1:8020/path/to/folder file:///mnt/gluster
>>>>>>>> This run maps on datanodes which have /mnt/gluster mounted on all of
>>>>>>>> them.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I don't know hadoop, so I'm of little help here. However it seems
>>>>>>> that
>>>>>>> -m
>>>>>>> 50
>>>>>>> means to execute 50 copies in parallel. This means that even if the
>>>>>>> distribution worked fine, at most 50 (much probably less) of the 78
>>>>>>> ec
>>>>>>> sets
>>>>>>> would be used in parallel.
>>>>>>>
>>>>>>>>
>>>>>>>>>>> This means that this is caused by some peculiarity of the
>>>>>>>>>>> mapreduce.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Yes but how a client write 500 files to gluster mount and those file
>>>>>>>> just written only to subset of subvolumes? I cannot use gluster as a
>>>>>>>> backup cluster if I cannot write with distcp.
>>>>>>>>
>>>>>>>
>>>>>>> All 500 files were created only on one of the 78 ec sets and the
>>>>>>> remaining
>>>>>>> 77 got empty ?
>>>>>>>
>>>>>>>>>>> You should look which files are created in each brick and how
>>>>>>>>>>> many
>>>>>>>>>>> while the process is running.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Files only created on nodes 185..204 or 205..224 or 225..244. Only
>>>>>>>> on
>>>>>>>> 20 nodes in each test.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> How many files there were in each brick ?
>>>>>>>
>>>>>>> Not sure if this can be related, but standard linux distributions
>>>>>>> have
>>>>>>> a
>>>>>>> default limit of 1024 open file descriptors. Having a so big volume
>>>>>>> and
>>>>>>> doing a massive copy, maybe this limit is affecting something ?
>>>>>>>
>>>>>>> Are there any error or warning messages in the mount or bricks logs ?
>>>>>>>
>>>>>>>
>>>>>>> Xavi
>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Apr 19, 2016 at 1:05 PM, Xavier Hernandez
>>>>>>>> <xhernandez at datalab.es>
>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hi Serkan,
>>>>>>>>>
>>>>>>>>> moved to gluster-users since this doesn't belong to devel list.
>>>>>>>>>
>>>>>>>>> On 19/04/16 11:24, Serkan Çoban wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I am copying 10.000 files to gluster volume using mapreduce on
>>>>>>>>>> clients. Each map process took one file at a time and copy it to
>>>>>>>>>> gluster volume.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I assume that gluster is used to store the intermediate files
>>>>>>>>> before
>>>>>>>>> the
>>>>>>>>> reduce phase.
>>>>>>>>>
>>>>>>>>>> My disperse volume consist of 78 subvolumes of 16+4 disk each. So
>>>>>>>>>> If
>>>>>>>>>> I
>>>>>>>>>> copy >78 files parallel I expect each file goes to different
>>>>>>>>>> subvolume
>>>>>>>>>> right?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> If you only copy 78 files, most probably you will get some
>>>>>>>>> subvolume
>>>>>>>>> empty
>>>>>>>>> and some other with more than one or two files. It's not an exact
>>>>>>>>> distribution, it's a statistially balanced distribution: over time
>>>>>>>>> and
>>>>>>>>> with
>>>>>>>>> enough files, each brick will contain an amount of files in the
>>>>>>>>> same
>>>>>>>>> order
>>>>>>>>> of magnitude, but they won't have the *same* number of files.
>>>>>>>>>
>>>>>>>>>> In my tests during tests with fio I can see every file goes to
>>>>>>>>>> different subvolume, but when I start mapreduce process from
>>>>>>>>>> clients
>>>>>>>>>> only 78/3=26 subvolumes used for writing files.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> This means that this is caused by some peculiarity of the
>>>>>>>>> mapreduce.
>>>>>>>>>
>>>>>>>>>> I see that clearly from network traffic. Mapreduce on client side
>>>>>>>>>> can
>>>>>>>>>> be run multi thread. I tested with 1-5-10 threads on each client
>>>>>>>>>> but
>>>>>>>>>> every time only 26 subvolumes used.
>>>>>>>>>> How can I debug the issue further?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> You should look which files are created in each brick and how many
>>>>>>>>> while
>>>>>>>>> the
>>>>>>>>> process is running.
>>>>>>>>>
>>>>>>>>> Xavi
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Apr 19, 2016 at 11:22 AM, Xavier Hernandez
>>>>>>>>>> <xhernandez at datalab.es> wrote:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Hi Serkan,
>>>>>>>>>>>
>>>>>>>>>>> On 19/04/16 09:18, Serkan Çoban wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Hi, I just reinstalled fresh 3.7.11 and I am seeing the same
>>>>>>>>>>>> behavior.
>>>>>>>>>>>> 50 clients copying part-0-xxxx named files using mapreduce to
>>>>>>>>>>>> gluster
>>>>>>>>>>>> using one thread per server and they are using only 20 servers
>>>>>>>>>>>> out
>>>>>>>>>>>> of
>>>>>>>>>>>> 60. On the other hand fio tests use all the servers. Anything I
>>>>>>>>>>>> can
>>>>>>>>>>>> do
>>>>>>>>>>>> to solve the issue?
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Distribution of files to ec sets is done by dht. In theory if you
>>>>>>>>>>> create
>>>>>>>>>>> many files each ec set will receive the same amount of files.
>>>>>>>>>>> However
>>>>>>>>>>> when
>>>>>>>>>>> the number of files is small enough, statistics can fail.
>>>>>>>>>>>
>>>>>>>>>>> Not sure what you are doing exactly, but a mapreduce procedure
>>>>>>>>>>> generally
>>>>>>>>>>> only creates a single output. In that case it makes sense that
>>>>>>>>>>> only
>>>>>>>>>>> one
>>>>>>>>>>> ec
>>>>>>>>>>> set is used. If you want to use all ec sets for a single file,
>>>>>>>>>>> you
>>>>>>>>>>> should
>>>>>>>>>>> enable sharding (I haven't tested that) or split the result in
>>>>>>>>>>> multiple
>>>>>>>>>>> files.
>>>>>>>>>>>
>>>>>>>>>>> Xavi
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>> Serkan
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> ---------- Forwarded message ----------
>>>>>>>>>>>> From: Serkan Çoban <cobanserkan at gmail.com>
>>>>>>>>>>>> Date: Mon, Apr 18, 2016 at 2:39 PM
>>>>>>>>>>>> Subject: disperse volume file to subvolume mapping
>>>>>>>>>>>> To: Gluster Users <gluster-users at gluster.org>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Hi, I have a problem where clients are using only 1/3 of nodes
>>>>>>>>>>>> in
>>>>>>>>>>>> disperse volume for writing.
>>>>>>>>>>>> I am testing from 50 clients using 1 to 10 threads with file
>>>>>>>>>>>> names
>>>>>>>>>>>> part-0-xxxx.
>>>>>>>>>>>> What I see is clients only use 20 nodes for writing. How is the
>>>>>>>>>>>> file
>>>>>>>>>>>> name to sub volume hashing is done? Is this related to file
>>>>>>>>>>>> names
>>>>>>>>>>>> are
>>>>>>>>>>>> similar?
>>>>>>>>>>>>
>>>>>>>>>>>> My cluster is 3.7.10 with 60 nodes each has 26 disks. Disperse
>>>>>>>>>>>> volume
>>>>>>>>>>>> is 78 x (16+4). Only 26 out of 78 sub volumes used during
>>>>>>>>>>>> writes..
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>
>>>
>
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