Pray that you have no issue with anything in the short term and that you don't lose power to the system while it is going on.
I did exactly as you are now and ended up with a corrupted filesystem due to what you are seeing. DO NOT interrupt it, or you may have big problems with filesystem integrity afterwards. See my previous posts to this list for details on what happened to me. On 14/07/2016 9:18 PM, Sébastien Luttringer wrote: > Hello, > > I have a performance issue with «btrfs replace» with raid5 and a _missing_ > device. My btrfs rely on 6x4TB HDD and the operating system is an Archlinux. > > In a nutshell, I will need 23 to 46 days to replace on missing disk. > > # btrfs fi sh /home > Label: 'raptor.home' uuid: 8739c8b2-110b-44ac-8b4d-285ad06ee446 > Total devices 7 FS bytes used 14.60TiB > devid 0 size 3.64TiB used 2.80TiB path /dev/sdf > devid 3 size 3.64TiB used 2.97TiB path /dev/sdh > devid 5 size 3.64TiB used 2.97TiB path /dev/sdc > devid 6 size 3.64TiB used 2.97TiB path /dev/sdd > devid 7 size 3.64TiB used 2.97TiB path /dev/sde > devid 8 size 3.64TiB used 2.97TiB path /dev/sdg > *** Some devices missing > > > At a disk full speed (100 MB/s) replacing the missing disk (4 TB) should take > around 8 hours. With the same disk model and same HBA card in another computer > with a mdadm/raid5, I could verify this duration could be reach. > > I also tested a «btrfs replace» without a missing disk and the speed was not > so > bad. Somewhere around half disk speed (50-60MB/s). Performances are under > mdadm. > > But, in my case, the drive is pass away, I can't use it as source of the > replace, so I have a replace speed of 1-2MB/s ! Which mean between 23-46 days > with bad usage performance and security risk. > > I tried to upgrade the kernel to the latest (4.7-rc6) but it's not better in > performance. I got some crash during replace with 4.6.0 which vanish with the > last rc. > > # iostat -md > Linux 4.7.0-rc6-seblu > (raptor.seblu.net) 14/07/2016 _x86_64_ (4 CPU) > > Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn > sdc 356,75 22,51 0,14 9132054 58427 > sdd 356,27 22,51 0,14 9131612 57094 > sde 361,53 22,52 0,14 9132207 57245 > sdf 362,78 0,00 1,81 4 735786 > sdg 357,82 22,51 0,14 9131763 58323 > sdh 325,25 22,52 0,14 9132715 58355 > > > So I have a really poor performance in rebuilding a raid5 mostly when the > replaced device is missing. > Is there a parameter to tweak of something I can do to improve the replace ? > > Regards, > -- Steven Haigh Email: net...@crc.id.au Web: https://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897
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