[tahoe-lafs-trac-stream] [tahoe-lafs] #1849: report maximum-immutable-share-size correctly in light of filesystem limits

[tahoe-lafs]

#1849: report maximum-immutable-share-size correctly in light of filesystem limits
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 Reporter:  zooko                          |          Owner:
     Type:  defect                         |         Status:  new
 Priority:  normal                         |      Milestone:  undecided
Component:  code-storage                   |        Version:  1.9.2
 Keywords:  easy scalability transparency  |  Launchpad Bug:
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 Currently storage servers report their {{{maximum-immutable-share-size}}}
 equal to their available disk space. This is not right for filesystems
 which limit filesize to a smaller size than the filesystem size, such as
 ext4, which limits files to 16 TB and filesystems to 1 EB.

 http://en.wikipedia.org/wiki/Comparison_of_filesystems#Limits

 To fix this ticket, make the disk backend report the filesize limit
 separately from the available space (probably by hardcoding the facts from
 wikipedia's table into it) and make the storage server cap its reported
 {{{maximum-immutable-share-size}}} according to that limit.

 The cloud storage backend has no hard limit on share size.

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1849>
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