On Tue, Jan 26, 2016 at 12:57 PM, Austin S. Hemmelgarn <ahferroin7@xxxxxxxxx> wrote: > 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. Which is most of what's on the volume unless the 4 disks were added and used for a while, but I can't tell what the time frame is. Anyway, it seems reasonable to try a balance without the filters to see if that's a factor, because those filters are brand new in btrfs-progs 4.4. Granted, I'd expect they've been tested by upstream developers, but I don't know if there's an fstest for balance with these specific filters yet. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
