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linux:fs:btrfs_multidisk [2017/05/19 08:40] niziak |
linux:fs:btrfs_multidisk [2021/02/16 21:07] (current) niziak |
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| ====== BTRFS on multiple devices ====== | ====== BTRFS on multiple devices ====== | ||
| + | |||
| + | [[https://serverfault.com/questions/814546/how-to-obtain-read-speeds-of-two-disks-using-mdadm-btrfs-raid1-or-zfs-mirror]] | ||
| ===== Encryption layout ===== | ===== Encryption layout ===== | ||
| Line 5: | Line 7: | ||
| ==== BTRFS on crypted devices ==== | ==== BTRFS on crypted devices ==== | ||
| | btrfs raid1 || | | btrfs raid1 || | ||
| - | | crypt | crypt | | + | | crypt | crypt | |
| - | | sda1 | sdb1 | | + | | sda1 | sdb1 | |
| * (-) Encryption has to be performed twice (no problem for modern CPUs) | * (-) Encryption has to be performed twice (no problem for modern CPUs) | ||
| - | * (+) Bitflips can be detected immediatelly and corrected by BTRFS | + | * (+) Bit-flips can be detected immediately and corrected by BTRFS |
| + | * (-) not possible to get benefit from hybrid RAID1 (mixed disc HDD & SSD) | ||
| + | |||
| + | |||
| + | ==== BTRFS on crypted devices with LVM ==== | ||
| + | |||
| + | | btrfs raid1 || | ||
| + | | crypt | crypt | | ||
| + | | LVM | LVM | | ||
| + | | (DM-Cache on fast SSD) || | ||
| + | | sda1 | sdb1 | | | ||
| + | |||
| + | * (-) Encryption has to be performed twice (no problem for modern CPUs) | ||
| + | * (+) Bit-flips can be detected immediately and corrected by BTRFS | ||
| + | * (-) not possible to get benefit from hybrid RAID1 (mixed disc HDD & SSD) | ||
| + | * (-) small overhead from LVM but | ||
| + | * (+) DM-cache with SSD disc can be used: [[https://www.redhat.com/en/blog/improving-read-performance-dm-cache]] | ||
| ==== BTRFS on soft RAID1 ==== | ==== BTRFS on soft RAID1 ==== | ||
| Line 18: | Line 36: | ||
| * (+) encryption performed only once (less CPU consumption) | * (+) encryption performed only once (less CPU consumption) | ||
| - | * (-) Bitflips detected only during raid1 scan. | + | * (-) Bit-flips detected only during RAID1 scan. |
| + | * (+) Benefits from hybrid RAID1 (SSH & HHD) using "writemostly" feature). See [[http://tansi.info/hybrid/]] | ||
| + | |||
| ===== Prepare 2nd disc ===== | ===== Prepare 2nd disc ===== | ||
| Line 41: | Line 62: | ||
| btrfs device add /dev/disc1/btrfs1 / | btrfs device add /dev/disc1/btrfs1 / | ||
| btrfs device usage / | btrfs device usage / | ||
| - | btrfs balance start -v -dconvert=raid1 -mconvert=raid1 / | + | nice ionice -c3 btrfs balance start -v -dconvert=raid1 -mconvert=raid1 -dsoft -msoft / |
| btrfs device usage / | btrfs device usage / | ||
| </code> | </code> | ||
| + | Note: "soft" filter will convert only chunks which are not already converted (usefull when previous balance was incomplete) | ||
| + | |||
| Make sure that data on both disc are the same. Especially system data are on both disc in RAID1 mode. | Make sure that data on both disc are the same. Especially system data are on both disc in RAID1 mode. | ||