XFS shrinking planned?
Hello all,
XFS is such a good high performance filesystem, kudos for that.
However for large filesystems (which are mainly those that require high performance) the ability to shrink would be really needed. People usually do not have double the space so to move files to a smaller XFS filesystem, and the inability of XFS to shrink forbids major reorganizations of the storage systems.
Currently, for that reason I use ext4. Performance is still decent and flexibility is higher due to the ability to shrink, but I would use XFS if it could shrink.
I suppose shrinking ability is not even planned, is it?
Thank you
S.
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Quoted 8 lines · Spelic
Hello all,
XFS is such a good high performance filesystem, kudos for that.However for large filesystems (which are mainly those that require high performance) the ability to shrink would be really needed. People usually do not have double the space so to move files to a smaller XFS filesystem, and the inability of XFS to shrink forbids major reorganizations of the storage systems.
Currently, for that reason I use ext4. Performance is still decent and flexibility is higher due to the ability to shrink, but I would use XFS if it could shrink.
I suppose shrinking ability is not even planned, is it?
Not formally planned, there are bits and pieces out there (i.e. the inode mover) which are part of what it might take to achieve a shrinker.
Another option, rather than fs shrinking, is to use the dm-thinp target, which would allow you to allocate a large-but-sparse block device, create a very large filesystem on that, and add or remove storage as needed. (At least I think you can remove it...!)
-Eric
Quoted 2 lines
Thank you
S.
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Quoted 9 lines · Eric Sandeen
Not formally planned, there are bits and pieces out there (i.e. the inode mover) which are part of what it might take to achieve a shrinker.
Another option, rather than fs shrinking, is to use the dm-thinp target, which would allow you to allocate a large-but-sparse block device, create a very large filesystem on that, and add or remove storage as needed. (At least I think you can remove it...!)
-Eric
Thanks for your reply Eric
Interesting technique, but for enforcing a maximum size (smaller than the very large allocated thin device) I would have to rely on quotas, which probably decreases performance. Then using thinp would mess up all the disk layout, basically replacing the XFS allocator, which most likely would decrease performances significantly. And then the thinp code itself is a medium performance thing and I don't think it can keep up with XFS performances, so that would presumably be a hard bottleneck. All this would result in a performance almost certainly lower than ext4.
Thanks
S.
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Quoted 9 lines · Spelic
Quoted 8 lines · Eric Sandeen
Not formally planned, there are bits and pieces out there (i.e. the inode mover) which are part of what it might take to achieve a shrinker.
Another option, rather than fs shrinking, is to use the dm-thinp target, which would allow you to allocate a large-but-sparse block device, create a very large filesystem on that, and add or remove storage as needed. (At least I think you can remove it...!)
Quoted 7 lines
Quoted 1 line
-Eric
Thanks for your reply Eric
Interesting technique, but for enforcing a maximum size (smaller than the very large allocated thin device) I would have to rely on quotas, which probably decreases performance.
"probably"
Quoted 3 lines
Then using thinp would mess up
all the disk layout, basically replacing the XFS allocator, which most likely would decrease performances significantly.
"most likely"
Quoted 4 lines
And then the
thinp code itself is a medium performance thing and I don't think it can keep up with XFS performances, so that would presumably be a hard bottleneck.
"presumably"
Quoted 2 lines
All this would result in a performance almost certainly lower than ext4.
"almost certainly..."
All possibilities, but possibly also worth testing to find out. ;) It's true that today the thinp allocator will impact XFS allocation patterns to some degree.
Anyway, shrink has been on the radar for years, it's just never really been a priority. It might happen some day...
-Eric
Quoted 3 lines
Thanks
S.
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