Re: Crashes running btrfs scrub

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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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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