On Fri, Dec 15 2017, guomingyang wrote: > Hi all: > > Today's disk is becoming larger and larger, and the recovery time > is becoming longer. I'm thinking about a lazy initialization mechanism > in linux raid5 to speed up recovery, which contains an un-initializing > bitmap and a backend thread for initializing stripes lazily only after a > stripe is write. The major difference is as follows: > > (1)When a raid4 or raid5 device is created, we don't recovery a > disk as usual, instead we just set all the bit in un-initialize bitmap. > > (2)When a write happens and the corresponding un-initializing bit > is set, we must first clean the bit, then wake up the backend thread to > resync the stripe, and only do RCW in corresponding stripe before the > resync is done. > > The major advantage of this mechanism is that when a disk is > replaced, we can only recovery the stripes which have been initialized, > so as to speed up recovery. > > Does linux-raid have similar mechanism today? Or is there anyone > who has already working on similar mechanism? > No, linux-raid doesn't support this. I don't know of anyone working on this. I wrote about the idea nearly 7 years ago http://neil.brown.name/blog/20110216044002#5 but never got around to doing anything. It probably wouldn't be too hard if someone wanted it enough to put in some effort. NeilBrown
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