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Difference between revisions of "Btrfs Maintenance"
ReadRateDegradation
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==== error ==== | ==== error ==== | ||
If btrfs encounters an unrecoverable error, such as a checksum mismatch, the filesystem | If btrfs encounters an unrecoverable error, such as a checksum mismatch, the filesystem will be mounted '''read-only'''. (When using RAID2, such errors are auto-repaired) | ||
==== clean ==== | ==== clean ==== | ||
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== Manual Maintenace == | == Manual Maintenace == | ||
From time to time it may be advisable to check the health of the volume. | From time to time it may be advisable to check the health of the volume. | ||
{{BoxInfo|Notice| Be aware, that with btrfs all maintenance is performed on a normally running system. The volume can be fully used. Even a shutdown during such an action is not problematic. Btrfs will continue to execute the action after the next boot until it completes.}} | |||
=== usage === | === usage === | ||
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==== check unallocated space ==== | ==== check unallocated space ==== | ||
{{RootCmd|command=btrfs filesystem usage -h /}} | {{RootCmd|command=btrfs filesystem usage -h /}} | ||
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If you have some space "free" on your volume, but the unallocated space is below 10% (or close to 10%), you can help btrfs to rebalance some chunks. | If you have some space "free" on your volume, but the unallocated space is below 10% (or close to 10%), you can help btrfs to rebalance some chunks. | ||
{{RootCmd|command=btrfs balance start -musage=50 -dusage=50}} | {{RootCmd|command=btrfs balance start -musage=50 -dusage=50 /}} | ||
Btrfs looks for chunks that contain more than 50% free space. It will take 2 of them and then move everything into a new chunk. After that, one chunk is released. This continues until each chunk is at least 50% full. | Btrfs looks for chunks that contain more than 50% free space. It will take 2 of them and then move everything into a new chunk. After that, one chunk is released. This continues until each chunk is at least 50% full. | ||
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If you have less than 20% unallocated space, please do the following: | If you have less than 20% unallocated space, please do the following: | ||
{{RootCmd|command=btrfs balance start -musage=75 -dusage=75}} | {{RootCmd|command=btrfs balance start -musage=75 -dusage=75 /}} | ||
Btrfs looks for chunks that are less than 75% full. | Btrfs looks for chunks that are less than 75% full. | ||
It will take 4 of them and then move everything into 3 new chunks. After that, one chunk can be released. This continues until each chunk is at least 75% full. | It will take 4 of them and then move everything into 3 new chunks. After that, one chunk can be released. This continues until each chunk is at least 75% full. | ||
If you still have less than 20% unallocated space, please do the following: | If you still have less than 20% unallocated space, please do the following: | ||
{{RootCmd|command=btrfs balance start -musage=90 -dusage=90}} | {{RootCmd|command=btrfs balance start -musage=90 -dusage=90 /}} | ||
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Tip:watch -d btrfs scrub status / | Tip:watch -d btrfs scrub status / | ||
== special cases == | |||
There seem to be some cases where additional maintenance is needed. | |||
==== ssd ==== | |||
===== Read Rate Degradation ===== | |||
This is not a problem of all ssd's in general, but only of some rare cases. Replacing the firmware solves the problem. | |||
A possibility to test the read-speed with btrfs is to read all data (scrub). If your ssd has this RRD-problem, a balance will help because it does rewrite all data to a new place. This can be done while the system is in use ! | |||
{{RootCmd|command=btrfs balance start --full-balance /}} | |||
This will take a long time. You can shutdown your pc whenever you want. Dont't be surprised. the balance will restart after boot until it is finished ! | |||
==== rotational disks ==== | |||
On rotational disks fragmentation may become a problem in some rare use cases. Then you can defragment your btrfs. | |||
===== de-fragmentation (not recommended) ===== | |||
This is NOT the same as defragmentation in older windows filesystems. Btrfs does NOT need defragmentation as normal maintenance. Do this only, if you can measure a huge loss of read-performance because a specific file/database is fragmented! | |||
* Only defragment these specific files. | |||
You have been warned ! | |||
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=See Also= | =See Also= | ||