On 02/07/2014 05:40 AM, Roman Mamedov wrote:
> On Thu, 06 Feb 2014 20:54:19 +0100
> Goffredo Baroncelli <kreij...@libero.it> wrote:
>
[...]
Even I am not entirely convinced, I update the Roman's PoC in order
to take in account all the RAID levels.
The filesystem test is composed by 7 51GB disks. Here my "df" results:
Profile: single
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 351G 512K 348G 1% /mnt/btrfs1
Profile: raid1
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 351G 1.3M 150G 1% /mnt/btrfs1
Profile: raid10
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 351G 2.3M 153G 1% /mnt/btrfs1
Profile: raid5
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 351G 2.0M 298G 1% /mnt/btrfs1
Profile: raid6
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 351G 1.8M 248G 1% /mnt/btrfs1
Note that RAID1 and RAID10 can only use an even number of disks.
The mixing mode (data and metadata in the same chunk)
return strange results.
Below my patch.
BR
G.Baroncelli
Changes history:
V1 First issue
V2 Correct a (old) bug when in RAID10 the disks aren't
a multiple of 4
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d71a11d..aea9afa 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1481,10 +1481,16 @@ static int btrfs_calc_avail_data_space(struct
btrfs_root *root, u64 *free_bytes)
num_stripes = nr_devices;
} else if (type & BTRFS_BLOCK_GROUP_RAID1) {
min_stripes = 2;
- num_stripes = 2;
+ num_stripes = nr_devices & ~1llu;
} else if (type & BTRFS_BLOCK_GROUP_RAID10) {
min_stripes = 4;
- num_stripes = 4;
+ num_stripes = nr_devices & ~1llu;
+ } else if (type & BTRFS_BLOCK_GROUP_RAID5) {
+ min_stripes = 3;
+ num_stripes = nr_devices;
+ } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
+ min_stripes = 4;
+ num_stripes = nr_devices;
}
if (type & BTRFS_BLOCK_GROUP_DUP)
@@ -1561,8 +1567,30 @@ static int btrfs_calc_avail_data_space(struct btrfs_root
*root, u64 *free_bytes)
if (devices_info[i].max_avail >= min_stripe_size) {
int j;
u64 alloc_size;
+ int k;
- avail_space += devices_info[i].max_avail * num_stripes;
+ /*
+ * Depending by the RAID profile, we use some
+ * disk space as redundancy:
+ * RAID1, RAID10, DUP -> half of space used as
redundancy
+ * RAID5 -> 1 stripe used as redundancy
+ * RAID6 -> 2 stripes used as redundancy
+ * RAID0,LINEAR -> no redundancy
+ */
+ if (type & BTRFS_BLOCK_GROUP_RAID1) {
+ k = num_stripes >> 1;
+ } else if (type & BTRFS_BLOCK_GROUP_DUP) {
+ k = num_stripes >> 1;
+ } else if (type & BTRFS_BLOCK_GROUP_RAID10) {
+ k = num_stripes >> 1;
+ } else if (type & BTRFS_BLOCK_GROUP_RAID5) {
+ k = num_stripes-1;
+ } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
+ k = num_stripes-2;
+ } else { /* RAID0/LINEAR */
+ k = num_stripes;
+ }
+ avail_space += devices_info[i].max_avail * k;
alloc_size = devices_info[i].max_avail;
for (j = i + 1 - num_stripes; j <= i; j++)
devices_info[j].max_avail -= alloc_size;
--
gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5
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