Difference between revisions of "Btrfs"

small corrections
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(small corrections)
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When not otherwise specified, additional devices are handled as '''J'''ust a '''B'''unch '''o'''f '''D'''isks (JBOD); this means  
When not otherwise specified, additional devices are handled as '''J'''ust a '''B'''unch '''o'''f '''D'''isks (JBOD); this means  
{{Info|In most cases it is advisable to use only one Btrfs volume}}  
{{BoxInfo|Tip|In most cases it is advisable to use '''only one volume'''}}  


=== move a volume to another disk ===
=== move a volume to another disk ===
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== snapshot ==
== snapshot ==
A snapshot looks nearly the same as a subvolume. But snapshots really are "read-only photographs of a subvolume". While the subvolume changes with time. The snapshot is frozen in the state of the subvolume at the time you made it.
A snapshot looks nearly the same as a subvolume. But snapshots really are "read-only photographs of a subvolume". While the subvolume changes with time. The snapshot is frozen in the state of the subvolume at the time you made it.
A snapshot is read-only. Therefore it is guaranteed not to change. In a snapshot you will find all files of the subvolume frozen in time. {{BoxWarning|where to place snapshots|When creating snapshots you have to watch out for the volume layout in use}}
A snapshot is read-only. Therefore it is guaranteed not to change. In a snapshot you will find all files of the subvolume frozen in time. {{BoxWarning|Where to place snapshots|When creating snapshots you have to watch out for the volume layout in use}}


Taking a snapshot is '''very fast''', and '''nearly priceless'''. After the snapshot is taken, all future writes will go as in CoW usual. But none of the space occupied by files in the snapshot will be reusable. As you write more and more new files the filesystem will grow because it can not reuse the files in the snapshot. A new snapshot will freeze additional all created or modified files since the last snapshot and so on. If you don´t release(delete) any snapshot you will eventually run out of space soon(disk full)
Taking a snapshot is '''very fast''', and '''nearly priceless'''. After the snapshot is taken, all future writes will go as in CoW usual. But none of the space occupied by files in the snapshot will be reusable. As you write more and more new files the filesystem will grow because it can not reuse the files in the snapshot. A new snapshot will freeze additional all created or modified files since the last snapshot and so on. If you don´t release(delete) any snapshot you will eventually run out of space soon(disk full)
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* Make the new subvolume the default
* Make the new subvolume the default


{{BoxDanger|Snapshots together with quotas|There are reports about massive problems when using '''quotas''' together with snapshots (snapper, timeshift)}}
{{BoxDanger|NO Snapshots together with quotas|There are reports about massive problems when using '''quotas''' together with snapshots (snapper, timeshift)}}
 
 
 


= Btrfs RAID =
= Btrfs RAID =
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