On 02/07/2014 05:40 AM, Roman Mamedov wrote:
> On Thu, 06 Feb 2014 20:54:19 +0100
> Goffredo Baroncelli <kreijack@xxxxxxxxx> wrote:
>
[...]
Even I am not entirely convinced, I update the Roman's PoC in order
to take in account all the RAID levels.
I performed some tests with 7 48.8GB disks. Here my "df" results
Profile: single
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 342G 512K 340G 1% /mnt/btrfs1
Profile: raid1
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 342G 1.3M 147G 1% /mnt/btrfs1
Profile: raid10
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 342G 2.3M 102G 1% /mnt/btrfs1
Profile: raid5
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 342G 2.0M 291G 1% /mnt/btrfs1
Profile: raid6
Filesystem Size Used Avail Use% Mounted on
/dev/vdc 342G 1.8M 243G 1% /mnt/btrfs1
Note that RAID1 can only uses 6 disks; raid 10 only four, but I think that it
is due to a previous bug.
Still the mixing mode (data and metadata raid in the same chunk) is unsupported
below my patch.
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d71a11d..e5c58b3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1485,6 +1485,12 @@ static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64 *free_bytes)
} else if (type & BTRFS_BLOCK_GROUP_RAID10) {
min_stripes = 4;
num_stripes = 4;
+ } 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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