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| author | David Sterba <dsterba@suse.com> | 2021-07-22 20:54:37 +0200 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2021-08-23 13:19:08 +0200 |
| commit | b2f78e88052bc0bee56bbf646d245fcfb431a873 (patch) | |
| tree | 57b7be2b327b87ce81c42e924dc856fdc893cbf0 | |
| parent | bd54f381a12ac695593271a663d36d14220215b2 (diff) | |
| download | linux-b2f78e88052bc0bee56bbf646d245fcfb431a873.tar.bz2 | |
btrfs: allow degenerate raid0/raid10
The data on raid0 and raid10 are supposed to be spread over multiple
devices, so the minimum constraints are set to 2 and 4 respectively.
This is an artificial limit and there's some interest to remove it.
Change this to allow raid0 on one device and raid10 on two devices. This
works as expected eg. when converting or removing devices.
The only difference is when raid0 on two devices gets one device
removed. Unpatched would silently create a single profile, while newly
it would be raid0.
The motivation is to allow to preserve the profile type as long as it
possible for some intermediate state (device removal, conversion), or
when there are disks of different size, with raid0 the otherwise
unusable space of the last device will be used too. Similarly for
raid10, though the two largest devices would need to be the same.
Unpatched kernel will mount and use the degenerate profiles just fine
but won't allow any operation that would not satisfy the stricter device
number constraints, eg. not allowing to go from 3 to 2 devices for
raid10 or various profile conversions.
Example output:
# btrfs fi us -T .
Overall:
Device size: 10.00GiB
Device allocated: 1.01GiB
Device unallocated: 8.99GiB
Device missing: 0.00B
Used: 200.61MiB
Free (estimated): 9.79GiB (min: 9.79GiB)
Free (statfs, df): 9.79GiB
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 3.25MiB (used: 0.00B)
Multiple profiles: no
Data Metadata System
Id Path RAID0 single single Unallocated
-- ---------- --------- --------- -------- -----------
1 /dev/sda10 1.00GiB 8.00MiB 1.00MiB 8.99GiB
-- ---------- --------- --------- -------- -----------
Total 1.00GiB 8.00MiB 1.00MiB 8.99GiB
Used 200.25MiB 352.00KiB 16.00KiB
# btrfs dev us .
/dev/sda10, ID: 1
Device size: 10.00GiB
Device slack: 0.00B
Data,RAID0/1: 1.00GiB
Metadata,single: 8.00MiB
System,single: 1.00MiB
Unallocated: 8.99GiB
Note "Data,RAID0/1", with btrfs-progs 5.13+ the number of devices per
profile is printed.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/volumes.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 8e61307ffad2..8526cc39faa9 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -38,7 +38,7 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = { .sub_stripes = 2, .dev_stripes = 1, .devs_max = 0, /* 0 == as many as possible */ - .devs_min = 4, + .devs_min = 2, .tolerated_failures = 1, .devs_increment = 2, .ncopies = 2, @@ -103,7 +103,7 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = { .sub_stripes = 1, .dev_stripes = 1, .devs_max = 0, - .devs_min = 2, + .devs_min = 1, .tolerated_failures = 0, .devs_increment = 1, .ncopies = 1, |