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The osd needs to know where it thought data was, in particular so it knows what it has. Then it gets the current map so it knows who to talk to so it can catch back up.
Sent from my iPhone
Hi, everyone.
I'm trying to read the source code that boots an OSD instance, and I find something really overwhelms me.
In the OSD::init() method, it read the OSDSuperblock by calling OSD::read_superblock(), and the it tried to get the "current" map : "osdmap = get_map(superblock.current_epoch)". Then OSD uses this osdmap to calculate the acting and up set of each pg.
I really don't understand this! Since the OSDSuperblock is read from the disk, the superblock.current_epoch should be an old epoch which is recorded by the last OSD instance that run on this directory. Why use an old "current_epoch" to calculate the acting
and up set of each pg?
Please help me, thank you:-)
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