[Gluster-users] Arbiter brick size estimation

[Oleksandr Natalenko]

Ravi,

here is the summary: [1]

Regards,
  Oleksandr.

[1] https://gist.github.com/e8265ca07f7b19f30bb3

On четвер, 17 березня 2016 р. 09:58:14 EET Ravishankar N wrote:
> On 03/16/2016 10:57 PM, Oleksandr Natalenko wrote:
> > OK, I've repeated the test with the following hierarchy:
> > 
> > * 10 top-level folders with 10 second-level folders each;
> > * 10 000 files in each second-level folder.
> > 
> > So, this composes 10×10×10000=1M files and 100 folders
> > 
> > Initial brick used space: 33 M
> > Initial inodes count: 24
> > 
> > After test:
> > 
> > * each brick in replica took 18G, and the arbiter brick took 836M;
> > * inodes count: 1066036
> > 
> > So:
> > 
> > (836 - 33) / (1066036 - 24) == 790 bytes per inode.
> > 
> > So, yes, it is slightly bigger value than with previous test due to, I
> > guess, lots of files in one folder, but it is still too far from 4k.
> > Given a good engineer should consider 30% reserve, the ratio is about 1k
> > per stored inode.
> > 
> > Correct me if I'm missing something (regarding average workload and not
> > corner cases).
> 
> Looks okay to me Oleksandr. You might want to make a github gist of your
> tests+results as a reference for others.
> Regards,
> Ravi
> 
> > Test script is here: [1]
> > 
> > Regards,
> > 
> >    Oleksandr.
> > 
> > [1] http://termbin.com/qlvz
> > 
> > On вівторок, 8 березня 2016 р. 19:13:05 EET Ravishankar N wrote:
> >> On 03/05/2016 03:45 PM, Oleksandr Natalenko wrote:
> >>> In order to estimate GlusterFS arbiter brick size, I've deployed test
> >>> setup
> >>> with replica 3 arbiter 1 volume within one node. Each brick is located
> >>> on
> >>> separate HDD (XFS with inode size == 512). Using GlusterFS v3.7.6 +
> >>> memleak
> >>> patches. Volume options are kept default.
> >>> 
> >>> Here is the script that creates files and folders in mounted volume: [1]
> >>> 
> >>> The script creates 1M of files of random size (between 1 and 32768
> >>> bytes)
> >>> and some amount of folders. After running it I've got 1036637 folders.
> >>> So, in total it is 2036637 files and folders.
> >>> 
> >>> The initial used space on each brick is 42M . After running script I've
> >>> got:
> >>> 
> >>> replica brick 1 and 2: 19867168 kbytes == 19G
> >>> arbiter brick: 1872308 kbytes == 1.8G
> >>> 
> >>> The amount of inodes on each brick is 3139091. So here goes estimation.
> >>> 
> >>> Dividing arbiter used space by files+folders we get:
> >>> 
> >>> (1872308 - 42000)/2036637 == 899 bytes per file or folder
> >>> 
> >>> Dividing arbiter used space by inodes we get:
> >>> 
> >>> (1872308 - 42000)/3139091 == 583 bytes per inode
> >>> 
> >>> Not sure about what calculation is correct.
> >> 
> >> I think the first one is right because you still haven't used up all the
> >> inodes.(2036637 used vs. the max. permissible 3139091). But again this
> >> is an approximation because not all files would be 899 bytes. For
> >> example if there are a thousand files present in a directory, then du
> >> <dirname> would be more than du <file> because the directory will take
> >> some disk space to store the dentries.
> >> 
> >>>    I guess we should consider the one
> >>> 
> >>> that accounts inodes because of .glusterfs/ folder data.
> >>> 
> >>> Nevertheless, in contrast, documentation [2] says it should be 4096
> >>> bytes
> >>> per file. Am I wrong with my calculations?
> >> 
> >> The 4KB is a conservative estimate considering the fact that though the
> >> arbiter brick does not store data, it still keeps a copy of both user
> >> and gluster xattrs. For example, if the application sets a lot of
> >> xattrs, it can consume a data block if they cannot be accommodated on
> >> the inode itself.  Also there is the .glusterfs folder like you said
> >> which would take up some space. Here is what I tried on an XFS brick:
> >> [root at ravi4 brick]# touch file
> >> 
> >> [root at ravi4 brick]# ls -l file
> >> -rw-r--r-- 1 root root 0 Mar  8 12:54 file
> >> 
> >> [root at ravi4 brick]# du file
> >> *0       file**
> >> *
> >> [root at ravi4 brick]# for i in {1..100}
> >> 
> >>   > do
> >>   > setfattr -n user.value$i -v value$i file
> >>   > done
> >> 
> >> [root at ravi4 brick]# ll -l file
> >> -rw-r--r-- 1 root root 0 Mar  8 12:54 file
> >> 
> >> [root at ravi4 brick]# du -h file
> >> *4.0K    file**
> >> *
> >> Hope this helps,
> >> Ravi
> >> 
> >>> Pranith?
> >>> 
> >>> [1] http://termbin.com/ka9x
> >>> [2]
> >>> http://gluster.readthedocs.org/en/latest/Administrator%20Guide/arbiter-v
> >>> o
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