Re: btrfs-progs 4.4 re-balance of RAID6 is very slow / limited to one cpu core?

[Christian Rohmann <crohmann@netcologne.de>]

Hey Chris and all,

On 01/25/2016 11:13 PM, Chris Murphy wrote:
> Does anyone suspect a kernel regression here? I wonder if its worth it
> to suggest testing the current version of all fairly recent kernels:
> 4.5.rc1, 4.4, 4.3.4, 4.2.8, 4.1.16? I think going farther back to
> 3.18.x isn't worth it since that's before the major work since raid56
> was added. Quite a while ago I've done a raid56 rebuild and balance
> that was pretty fast but it was only a 4 or 5 device test.

Problem is that this balance did not work before going to 4.4 kernel,
it's was simply crashing after about an hour or two of runtime.

Currently I am using 4.4 kernel + btrfs-progs, so apart from 4.5rc1 I
can not get any more bleeding edge.

4.5 I am happy to try, but not RC1 as there are already some bugs
popping up regarding the BTRFS changes.


On 01/26/2016 07:14 AM, Chris Murphy wrote:
> Christian, what are you getting for 'iotop -d3 -o' or 'iostat -d3'. Is
> it consistent or is it fluctuating all over the place? What sort of
> eyeball avg/min/max are you getting?

"1672.81 K/s 1672.81 K/s  0.00 %  6.99 % btrfs balance start -dstripes
1..11 -mstripes 1..11 "

but it's jumping up to 25MB/s for a few polls, but most of the time it's
at 1.3 to 1.7 MB/s


You may check out more the various munin graphs of the box if you like:
 * http://mirror.netcologne.de/munin

has all the goods.
This also brings me to mention, that the disks (it's 12 disks though!)
read somewhere between 20 and 60MB/s constantly.




Regards

Christian