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I searched the github page and this HN comment thread for the string "frag" and got nothing ... I don't know if the authors are here, but if they are - would y

by rsync 9y ago

I searched the github page and this HN comment thread for the string "frag" and got nothing ... I don't know if the authors are here, but if they are - would you comment on fragmentation and the dangers of growing a filesystem past 95-98% full ? In the world of ZFS, performance can become significantly degraded with as low as 90% space filled. Further, our experience has been that you can permanently degrade filesystem performance by churning the usage above 95% for any significant amount of time. Which is to say, even if you reduce usage back down to 80%, the zpool maintains poor performance until it is destroyed and recreated. This is exactly what you would expect to see with a fragmenting filesystem that has no defrag tool. Unfortunately, creating a defrag tool for ZFS is a very daunting technical hurdle and it appears that nobody is interested in pursuing it. How does TFS behave ? Does it have, or do you plan for it to have, a defrag utility ?

ticki_ 9y ago
Author here. > I don't know if the authors are here, but if they are - would you comment on fragmentation and the dangers of growing a filesystem past 95-98% full ? Fragmentation isn't an issue in TFS, at all. Because it is a cluster-based file system. Essentially that means that files aren't stored contagiously, but instead in small chunks. The allocation is done entirely on the basis of unrolled freelists. This does cause a slight space overhead (only slight, coming from the fact that metadata of the file is stored in the full form), but it completely eliminates any fragmentation.
- gpm 9y ago
  I only have a basic understanding of harddisks/filesystems, but won't that slow down reading/writing on harddisks since the chunks won't be in order and close together?
  - ticki_ 9y ago
    With modern hard disks, no. They work in sectors.
    - amadvance 9y ago
      I suppose you mean SSD disks. Rotating disks are surely affected by not contiguous operations, even if done with sector granularity.
- asymmetric 9y ago
  > files aren't stored contagiously I think you mean contiguously.

by rsync 9y ago

ticki_ 9y ago

Author here. > I don't know if the authors are here, but if they are - would you comment on fragmentation and the dangers of growing a filesystem past 95-98% full ? Fragmentation isn't an issue in TFS, at all. Because it is a cluster-based file system. Essentially that means that files aren't stored contagiously, but instead in small chunks. The allocation is done entirely on the basis of unrolled freelists. This does cause a slight space overhead (only slight, coming from the fact that metadata of the file is stored in the full form), but it completely eliminates any fragmentation.

gpm 9y ago
I only have a basic understanding of harddisks/filesystems, but won't that slow down reading/writing on harddisks since the chunks won't be in order and close together?
- ticki_ 9y ago
  With modern hard disks, no. They work in sectors.
  - amadvance 9y ago
    I suppose you mean SSD disks. Rotating disks are surely affected by not contiguous operations, even if done with sector granularity.
asymmetric 9y ago
> files aren't stored contagiously I think you mean contiguously.