xfs
[Top] [All Lists]

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

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: Is XFS suitable for 350 million files on 20TB storage?
From: Stefan Priebe <s.priebe@xxxxxxxxxxxx>
Date: Fri, 05 Sep 2014 20:07:38 +0200
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140905134810.GA3965@xxxxxxxxxxxxxx>
References: <540986B1.4080306@xxxxxxxxxxxx> <20140905123058.GA29710@xxxxxxxxxxxxxxx> <5409AF40.10801@xxxxxxxxxxxx> <20140905134810.GA3965@xxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0
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

<Prev in Thread] Current Thread [Next in Thread>