[lxc-users] Limiting disk IO on LXD containers [solved]

[Ivan Ogai]

Addition for people interested on I/O limits on mdadm RAIDs (software
RAIDs):

Currently I/O limits doesn't work on mdadm RAIDs. An issue for
supporting it has been opened at

https://github.com/lxc/lxd/issues/3515


* Ivan Ogai <lxc-users at ogai.name> [2017-07-06 12:30]:
> Simos has already answered this question on 
> 
> https://discuss.linuxcontainers.org/t/limiting-disk-io-on-lxd-containers/261
> 
> I have also copied the answer on 
> https://serverfault.com/questions/858873/limiting-disk-io-on-lxd-containers
> 
> In short: it works wtih ZFS and btrfs storage backend.
> 
> 
> * Ivan Ogai <lxc-users at ogai.name> [2017-07-04 16:38]:
> > Greetings LXCers/LXDers
> > 
> > Just in case: I have also posted this question in discuss and
> > serverfault. By getting an answer here or there, I will answer the
> > others of course for everyone to find them. References at the end.
> > 
> > 
> > I have tried without success to limit the disk IO of a LXD container named *ci* with:
> > 
> >     lxc config device set ci root limits.read  30MB
> >     lxc config device set ci root limits.write 10MB
> > 
> > However, when running e.g. this command on the container:
> > 
> >     dd if=/dev/zero of=/root/testfile bs=1G count=10 oflag=direct
> > 
> > the result is the whole capicity of the disk, which is about **130MB/s**, instead of the expected result of about **10MB/s** for writing operations:
> > 
> >     10737418240 bytes (11 GB, 10 GiB) copied, 81,3877 s, 132 MB/s
> > 
> > This is also confirmed by `atop` running on the host.
> > 
> > **How can I effectively limit the disk IO of the container, so that no matter what happens on it, the host disk performance is not overcommitted**?
> > 
> > On a second test, I run the same *dd* command as above at the same time on the
> > guest and on the host, but the host is not prioritized either.
> > 
> > 
> > Some additional information:
> > 
> > - Host and guest are Ubuntu 16.04
> > - The server has two hard disks with equal partitions, joined in RAID 1 arrays
> > - On top of the biggest RAID array the root filesystem is mounted on a LVM volume group
> > 
> >         root at server ~ # lvs
> >         LV   VG   Attr       LSize
> >         root vg0  -wi-ao---- 2,72t
> >         swap vg0  -wi-ao---- 4,00g
> > 
> > - The LXD storage backend is *dir*
> > 
> > I could partitition the disk differently if that could help limiting disk IO of the container, e.g. having a RAID array dedicated to ZFS for LXD. **Would that help**?
> > 
> > 
> > Question references:
> > https://discuss.linuxcontainers.org/t/limiting-disk-io-on-lxd-containers/261
> > https://serverfault.com/questions/858873/limiting-disk-io-on-lxd-containers
> > 
> > -- 
> > Ivan
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