Re: Filesystem Went Read Only During Raid-10 to Raid-6 Data Conversion

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On 2020-07-20 18:57, Goffredo Baroncelli wrote:
On 7/18/20 12:36 PM, Steven Davies wrote:
On 17/07/2020 06:57, Zygo Blaxell wrote:
On Thu, Jul 16, 2020 at 09:11:17PM -0400, John Petrini wrote:

--snip--

/dev/sdf, ID: 12
    Device size:             9.10TiB
    Device slack:              0.00B
    Data,RAID10:           784.31GiB
    Data,RAID10:             4.01TiB
    Data,RAID10:             3.34TiB
    Data,RAID6:            458.56GiB
    Data,RAID6:            144.07GiB
    Data,RAID6:            293.03GiB
    Metadata,RAID10:         4.47GiB
    Metadata,RAID10:       352.00MiB
    Metadata,RAID10:         6.00GiB
    Metadata,RAID1C3:        5.00GiB
    System,RAID1C3:         32.00MiB
    Unallocated:            85.79GiB

[...]

RFE: improve 'dev usage' to show these details.

As a user I'd look at this output and assume a bug in btrfs-tools because of the repeated conflicting information.

What would be the expected output ?
What about the example below ?

 /dev/sdf, ID: 12
     Device size:             9.10TiB
     Device slack:              0.00B
     Data,RAID10:           784.31GiB
     Data,RAID10:             4.01TiB
     Data,RAID10:             3.34TiB
     Data,RAID6[3]:         458.56GiB
     Data,RAID6[5]:         144.07GiB
     Data,RAID6[7]:         293.03GiB
     Metadata,RAID10:         4.47GiB
     Metadata,RAID10:       352.00MiB
     Metadata,RAID10:         6.00GiB
     Metadata,RAID1C3:        5.00GiB
     System,RAID1C3:         32.00MiB
     Unallocated:            85.79GiB

That works for me for RAID6. There are three lines for RAID10 too - what's the difference between these?

Another possibility (but the output will change drastically, I am
thinking to another command)

Filesystem '/'
	Data,RAID1:		123.45GiB
		/dev/sda	 12.34GiB
		/dev/sdb	 12.34GiB
	Data,RAID1:		123.45GiB
		/dev/sde	 12.34GiB
		/dev/sdf	 12.34GiB

Is this showing that there's 123.45GiB of RAID1 data which is mirrored between sda and sdb, and 123.45GiB which is mirrored between sde and sdf? I'm not sure how useful that would be if there are a lot of disks in a RAID1 volume with different blocks mirrored between different ones. For RAID1 (and RAID10) I would keep it simple.

	Data,RAID6:		123.45GiB
		/dev/sda	 12.34GiB
		/dev/sdb	 12.34GiB
		/dev/sdc	 12.34GiB
	Data,RAID6:		123.45GiB
		/dev/sdb	 12.34GiB
		/dev/sdc	 12.34GiB
		/dev/sdd	 12.34GiB
		/dev/sde	 12.34GiB
		/dev/sdf	 12.34GiB

Here there would need to be something which shows what the difference in the RAID6 blocks is - if it's the chunk size then I'd do the same as the above example with e.g. Data,RAID6[3].

The number are the chunks sizes (invented). Note: for RAID5/RAID6 a
chunk will uses near all disks; however for (e.g.) RAID1  there is the
possibility that CHUNKS use different disks pairs (see the two RAID1
instances).

--
Steven Davies



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