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doc: mention new invalid states in lvmetad_design

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David Teigland 2015-06-23 16:48:28 -05:00
parent c23e7ff2a0
commit ba2b701f2c
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doc/lvmetad_design.txt
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@ -137,6 +137,17 @@ hosts. Overall, this is not hard, but the devil is in the details. I would
possibly disable lvmetad for clustered volume groups in the first phase and
only proceed when the local mode is robust and well tested.
With lvmlockd, lvmetad state is kept up to date by flagging either an
individual VG as "invalid", or the global state as "invalid". When either
the VG or the global state are read, this invalid flag is returned along
with the data. The client command can check for this invalid state and
decide to read the information from disk rather than use the stale cached
data. After the latest data is read from disk, the command may choose to
send it to lvmetad to update the cache. lvmlockd uses version numbers
embedded in its VG and global locks to detect when cached data becomes
invalid, and it then tells lvmetad to set the related invalid flag.
dct, 2015-06-23
Protocol & co.
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