Open Stack

Hi Robert,

I was reading your post and is interesting because we have similar swift
deployments and uses cases.
We are storing millons of small images in our swift cluster, 32 Storage
nodes w/12 - 2TB HDD + 2 SSD each one, and we are having an total average
of 200k rpm in whole cluster.
In terms of % of util. of our disks,  we have an average of 50% of util in
all our disks but we just are using a 15% of the total capacity of them.
When I look at used inodes on our object nodes with "df -i" we hit about 17
million inodes per disk.

So it seems a big number of inodes considering that we are using just a 15%
of the total capacity. A different thing here is that we are using 512K of
inode size and we have a big amount of memory .
Also we always have one of our disks close to 100% of util, and this is
caused by the object-auditor that scans all our disks continuously.

So we was also thinking in the possibility to change the kind of disks that
we are using, to use smaller and faster disks.
Will be really util to know what kind of disks are you using in your old
and new storage nodes, and compare that with our case.


Cheers,
Max

*
*

*Maximiliano Venesio *
#melicloud CloudBuilders
Arias 3751, Piso 7 (C1430CRG)
Ciudad de Buenos Aires - Argentina
Cel: +549(11) 15-3770-1853
Tel : +54(11) 4640-8411


On Tue, Aug 6, 2013 at 11:54 AM, Robert van Leeuwen <
Robert.vanLeeuwen at spilgames.com> wrote:

> Could you check your disk IO on the container /object nodes?
>
> We have quite a lot of files in swift and for comparison purposes I played
> a bit with COSbench to see where we hit the limits.
> We currently max out at about 200 - 300 put request/second and the
> bottleneck is the disk IO on the object nodes
> Our account / container nodes are on SSD's and are not a limiting factor.
>
> You can look for IO bottlenecks with e.g. "iostat -x 10" (this will
> refresh the view every 10 seconds.)
> During the benchmark is see some of the disks are hitting 100% utilization.
> That it is hitting the IO limits with just 200 puts a second has to do
> with the number of files on the disks.
> When I look at used inodes on our object nodes with "df -i" we hit about
> 60 million inodes per disk.
> (a significant part of that are actually directories I calculated about 30
> million files based on the number of files in swift)
> We use flashcache in front of those disks and it is still REALLY slow,
> just doing a "ls" can take up to 30 seconds.
> Probably adding lots of memory should help caching the inodes in memory
> but that is quite challenging:
> I am not sure how big a directory is in the xfs inode tree but just the
> files:
> 30 million x 1k inodes =  30GB
> And that is just one disk :)
>
> We still use the old recommended inode size of 1k and the default of 256
> can be used now with recent kernels:
> https://lists.launchpad.net/openstack/msg24784.html
>
> So sometime ago we decided to go for nodes with more,smaller & faster
> disks with more memory.
> Those machines are not even close to their limits however we still have
> more "old" nodes
> so performance is limited by those machines.
> At this moment it is sufficient for our use case but I am pretty confident
> we would be able to
> significantly improve performance by adding more of those machines and
> doing some re-balancing of the load.
>
> Cheers,
> Robert van Leeuwen
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