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Read/Write Replication: WaR1 policy: read() requires a successfully acquired lease #235

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lkairies opened this issue Jun 3, 2014 · 2 comments

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commented Jun 3, 2014

From michael....@gmail.com on November 30, 2011 10:56:15

What steps will reproduce the problem? 1. Setup a XtreemFS system with two OSDs and set the default replication policy for the volume to "WaR1" and the replication factor to 2.
2. Write data into a file.
3. Kill one OSD.
4. Try to read the file content. What is the expected output? What do you see instead? According to the WaR1 description, the read() should succeed as there is one available replica left.

However, the current implementation does try to acquire a lease in this case and this does fail as no majority is present, the read() does fail.

In case of a WaR1 read(), execute a local read() only. If a write() follows, upgrade the file state in the OSD and acquire the lease first before executing the write().

Original issue: http://code.google.com/p/xtreemfs/issues/detail?id=235

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commented Jun 3, 2014

From jas...@alumni.cmu.edu on July 24, 2013 15:44:42

Does this happen with WqRq as well?

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commented Jun 3, 2014

From michael....@gmail.com on August 13, 2013 09:20:33

Yes, but for WqRq a lease is required anyway, also for read()ing. That's because WqRq requires a majority to be always available.

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