On 2016-01-26 14:26, Chris Murphy wrote:
On Tue, Jan 26, 2016 at 1:54 AM, Christian Rohmann
<crohmann@xxxxxxxxxxxxx> wrote:
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
That is really slow. The fact you can't balance without crashing prior
to a 4.4 kernel makes me suspicious about the file system state. What
about reading and writing files? What's the performance in that case?
Is it just the balance that's this slow? Do you have the call traces
for older kernel crashes with balance? What btrfs-progs was used to
create the raid6 volume?
Maybe the slowness is due to the -dstripes -mstripes filter. That's
relatively new. And I didn't try that. And I also don't really
understand the values you picked either. Seems to me if you've added
four drives relatively recently, there won't be many chunks using
12-strip stripes, most of them will be 8-strip stripes. So I don't
really know what you're limiting.
The filters he used are telling balance to re-stripe anything spanning
less than 12 devices. So, in essence, it's only going to re-stripe the
chunks from before the fourth disk was added.
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