Re: Is XFS suitable for 350 million files on 20TB storage?

[Stefan Priebe <s.priebe@profihost.ag>]

Hi,

Am 05.09.2014 15:48, schrieb Brian Foster:
> On Fri, Sep 05, 2014 at 02:40:32PM +0200, Stefan Priebe - Profihost AG wrote:
>>
>> Am 05.09.2014 um 14:30 schrieb Brian Foster:
>>> On Fri, Sep 05, 2014 at 11:47:29AM +0200, Stefan Priebe - Profihost AG wrote:
>>>> Hi,
>>>>
>>>> i have a backup system running 20TB of storage having 350 million files.
>>>> This was working fine for month.
>>>>
>>>> But now the free space is so heavily fragmented that i only see the
>>>> kworker with 4x 100% CPU and write speed beeing very slow. 15TB of the
>>>> 20TB are in use.
>>>>
>>>> Overall files are 350 Million - all in different directories. Max 5000
>>>> per dir.
>>>>
>>>> Kernel is 3.10.53 and mount options are:
>>>> noatime,nodiratime,attr2,inode64,logbufs=8,logbsize=256k,noquota
>>>>
>>>> # xfs_db -r -c freesp /dev/sda1
>>>>     from      to extents  blocks    pct
>>>>        1       1 29484138 29484138   2,16
>>>>        2       3 16930134 39834672   2,92
>>>>        4       7 16169985 87877159   6,45
>>>>        8      15 78202543 999838327  73,41
>>>>       16      31 3562456 83746085   6,15
>>>>       32      63 2370812 102124143   7,50
>>>>       64     127  280885 18929867   1,39
>>>>      256     511       2     827   0,00
>>>>      512    1023      65   35092   0,00
>>>>     2048    4095       2    6561   0,00
>>>>    16384   32767       1   23951   0,00
>>>>
>>>> Is there anything i can optimize? Or is it just a bad idea to do this
>>>> with XFS? Any other options? Maybe rsync options like --inplace /
>>>> --no-whole-file?
>>>>
>>>
>>> It's probably a good idea to include more information about your fs:
>>>
>>> http://xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F
>>
>> Generally sure but the problem itself is clear. If you look at the free
>> space allocation you see that free space is heavily fragmented.
>>
>> But here you go:
>> - 3.10.53 vanilla
>> - xfs_repair version 3.1.11
>> - 16 cores
>> - /dev/sda1 /backup xfs
>> rw,noatime,nodiratime,attr2,inode64,logbufs=8,logbsize=256k,noquota 0 0
>> - Raid 10 with 1GB controller cache running in write back mode using 24
>> spinners
>> - no lvm
>> - no io waits
>> - xfs_info /serverbackup/
>> meta-data=/dev/sda1              isize=256    agcount=21,
>> agsize=268435455 blks
>>           =                       sectsz=512   attr=2
>> data     =                       bsize=4096   blocks=5369232896, imaxpct=5
>>           =                       sunit=0      swidth=0 blks
>> naming   =version 2              bsize=4096   ascii-ci=0
>> log      =internal               bsize=4096   blocks=521728, version=2
>>           =                       sectsz=512   sunit=0 blks, lazy-count=1
>> realtime =none                   extsz=4096   blocks=0, rtextents=0
>>
>> anything missing?
>>
>
> What's the workload to the fs? Is it repeated rsync's from a constantly
> changing dataset? Do the files change frequently or are they only ever
> added/removed?

Yes it repeated rsync with constant changing files. About 10-20% of all 
files every week. A mixture of changing, removing / adding.

> Also, what is the characterization of writes being "slow?" An rsync is
> slower than normal? Sustained writes to a single file? How significant a
> degradation?

kworker is using all cpu while writing data to this xfs partition. rsync 
can just write at a rate of 32-128kb/s.

> Something like the following might be interesting as well:
> for i in $(seq 0 20); do xfs_db -c "agi $i" -c "p freecount" <dev>; done
freecount = 3189417
freecount = 1975726
freecount = 1309903
freecount = 1726846
freecount = 1271047
freecount = 1281956
freecount = 1571285
freecount = 1365473
freecount = 1238118
freecount = 1697011
freecount = 1000832
freecount = 1369791
freecount = 1706360
freecount = 1439165
freecount = 1656404
freecount = 1881762
freecount = 1593432
freecount = 1555909
freecount = 1197091
freecount = 1667467
freecount = 63

Thanks!

Stefan



> Brian
>
>>> ... as well as what your typical workflow/dataset is for this fs. It
>>> seems like you have relatively small files (15TB used across 350m files
>>> is around 46k per file), yes?
>>
>> Yes - most fo them are even smaller. And some files are > 5GB.
>>
>>> If so, I wonder if something like the
>>> following commit introduced in 3.12 would help:
>>>
>>> 133eeb17 xfs: don't use speculative prealloc for small files
>>
>> Looks interesting.
>>
>> Stefan

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