Sorry, sir. I don't quite follow you. I agree that the osds must get the current map to know who to contact so it can catch up. But it looks to me that the osd is getting the current map through get_map(superblock.current_epoch) in which the variable superblock.current_epoch is read from the disk by OSD::read_superblock at boot time and has't been updated by a monitor, which means it is not the real curent epoch. How can OSD get the current map using an old epoch?
Sent from my Mi phone
On David Turner <david.turner@xxxxxxxxxxxxxxxx>, Oct 23, 2016 12:34 AM wrote:
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 iPhoneHi, 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.聽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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