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I suppose you could patch in PAR encoding for data, would that be significantly different than specifying copies=N for data and/or making multiple pools single
by jakeogh 7y ago
I suppose you could patch in PAR encoding for data, would that be significantly different than specifying copies=N for data and/or making multiple pools single disk and raiding them?
- ghusbands 7y agoPAR encoding is much more space-efficient than storing multiple copies, though using it efficiently would be really tricky. Though not more tricky than most other filesystem development. If you can indeed RAID-z multiple pools across a single disk, that would give many of the same advantages, without having to duplicate everything. Obviously, it would also greatly affect performance, with every IO operation becoming N operations against one disk.
- jakeogh 6y agoWhy would PAR be tricky to use efficiently? I just see it as a file encoding.
- ghusbands 6y agoIt's only a file encoding if you do it per file, but that removes a lot of the advantages of sharing and minimising the recovery data. PAR is usually across multiple files/blocks, but then you've got to manage this extra data when any part of any of those files/blocks changes. The more complete/parallel your recovery data is, the more you need to update on even a small change to one file. There'd be all sorts of ways to make it more efficient, but it would take some analysis to work out the best trade-offs.