On Thu, Jan 17, 2013 at 03:39:40AM -0800, Kent Overstreet wrote: > Suppose I could fill out the bcache version... > > On Thu, Jan 17, 2013 at 05:52:00PM +0800, Amit Kale wrote: > > 11. Error conditions - Handling power failures, intermittent and permanent device failures. > > Power failures and device failures yes, intermittent failures are not > explicitly handled. Coworker pointed out bcache actually does handle some intermittent io errors. I just added error handling to the documentation: http://atlas.evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt?h=bcache-dev To cut and paste, Bcache tries to transparently handle IO errors to/from the cache device without affecting normal operation; if it sees too many errors (the threshold is configurable, and defaults to 0) it shuts down the cache device and switches all the backing devices to passthrough mode. - For reads from the cache, if they error we just retry the read from the backing device. - For writethrough writes, if the write to the cache errors we just switch to invalidating the data at that lba in the cache (i.e. the same thing we do for a write that bypasses the cache) - For writeback writes, we currently pass that error back up to the filesystem/userspace. This could be improved - we could retry it as a write that skips the cache so we don't have to error the write. - When we detach, we first try to flush any dirty data (if we were running in writeback mode). It currently doesn't do anything intelligent if it fails to read some of the dirty data, though. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
