#1793 closed enhancement (fixed)
Clarified risks of shares.happy <= shares.needed in configuration.rst
| Reported by: | Sagi | Owned by: | marlowe |
|---|---|---|---|
| Priority: | minor | Milestone: | undecided |
| Component: | documentation | Version: | 1.9.2 |
| Keywords: | preservation, docs | Cc: | |
| Launchpad Bug: |
Description
< Sagi> suppose I currently have 3 nodes online. When I set N=6,K=H=3, every
node gets two shares. Now if one fails, I still have my data
< Sagi> in addition, one of the shares on the remaining two can get corrupted.
< zooko> Sagi: right.
< Sagi> configuration.rst says "A value of shares.happy <= k is allowed, but
does not provide any redundancy if some servers fail or lose shares."
< Sagi> that is incorrect for this situation, then.
< Sagi> I think that sentence is only correct when gridsize >= N
< zooko> Sagi, I believe you are exactly correct.
Attachments (1)
Change History (6)
Changed at 2012-07-12T19:38:23Z by Sagi
comment:1 Changed at 2012-07-12T19:39:26Z by Sagi
- Summary changed from Clarified risks of shares.happy - shares.needed in configuration.rst to Clarified risks of shares.happy <= shares.needed in configuration.rst
comment:2 Changed at 2012-07-12T19:47:43Z by davidsarah
comment:3 Changed at 2012-07-12T20:31:04Z by david-sarah@…
- Resolution set to fixed
- Status changed from new to closed
In 9a6fb895459b3b93:
comment:4 Changed at 2012-07-16T00:43:13Z by david-sarah <david-sarah@…>
In 9a6fb895459b3b93:
comment:5 Changed at 2012-07-20T03:55:01Z by david-sarah@…
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So, if shares.happy <= k, whether there is any redundancy depends on the share distribution. It is not the case in general that for N=6, k=H=3, each server is guaranteed to have 2 shares initially. That's what will happen if everything is working correctly (all servers have free space, no failures during upload), but the upload can still succeed without that being true.