On 2018年03月21日 01:44, Mike Stevens wrote: > >>> 30 devices is really not that much, heck you get 90 disks top load JBOD >>> storage chassis these days and BTRFS does sound like an attractive choice >>> for things like that. > >> So Mike's case is, that both metadata and data are configured as >> raid6, and the operations, balance and scrub, that he tried, need to >> set the existing block group as readonly (in order to avoid any >> further changes being applied during operations are running), then we >> got into the place where another system chunk is needed. > >> However, I think it'd be better to have some warnings about this when >> doing a) mkfs.btrfs -mraid6, b) btrfs device add. > >> David, any idea? > > I'll certainly vote for a warning, I would have set this up differently had I > been aware. > > My filesystem check seems to have returned successfully: > > [root@auswscs9903] ~ # btrfs check --readonly /dev/sdb > Checking filesystem on /dev/sdb > UUID: 77afc2bb-f7a8-4ce9-9047-c031f7571150 > checking extents > checking free space cache > checking fs roots > checking csums > checking root refs > found 97926270238720 bytes used err is 0 > total csum bytes: 95395030288 > total tree bytes: 201223503872 > total fs tree bytes: 84484636672 > total extent tree bytes: 7195869184 > btree space waste bytes: 29627784154 > file data blocks allocated: 97756261568512 > > I've remounted the filesystem and I can at least touch a file. I'm > restarting the rsync that was running when it originally went read only. > What is the next step if it drops back to r/o?
As already mentioned, if you're using tons of disks and RAID0/10/5/6 as
metadata profile, you can just convert your metadata (or just system) to
RAID1/DUP.
Then there will be more than enough space for system chunk array.
Thanks,
Qu
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