On 11/03/19 22:37, Adam Goryachev wrote: > On 12/3/19 5:14 am, Wols Lists wrote: >> On 11/03/19 12:31, Nix wrote: >>> On 10 Mar 2019, Wols Lists uttered the following: >>> >>>>> I'd like to modify the raid layer such that it times out quickly, and >>>>> recalculates and rewrites the data after a few seconds, such that >>>>> these >>>>> drives cease to be a problem, but stick that on the long list of raid >>>>> papercuts I'd like to sort out when I can find the time to learn to >>>>> program the raid subsystem! >>> I don't see how that could work. When these drives get stuck on lengthy >>> retries, they are essentially unresponsive: >> So any code needs to take that in to account. Pain in the arse, but when >> the linux read times out, the re-write code needs to detect that the >> drive is one of these cheapos, and spawn a thread that waits for the >> drive time-out before rewriting it. >> >> Of course, that's going to cause a host of other issues that will need >> sorting/fixing :-) - the obvious one is what happens if something else >> re-writes that block in the middle of the time-out period ... >> >> Cheers, >> Wol > > Doesn't this happen already? The drive will either return the data (if > it magically succeeds in reading the requested data in that 180? > seconds, or it will return a read error. But that's the whole point - THAT IS UNACCEPTABLE. What I would like to make happen is that 1) Linux issues a read request ... we have a read error so 2) Linux times out after 7 seconds 3) The raid code computes the missing block and passes it back to the user 4) The raid code spots that the disk has a 180 timeout *so it waits* 5) The block is rewritten. You're missing the point that that 180s wait really f***s things up for people, and/or they don't realise that there's a problem until they hit it. My solution is a very good fix apart from the fact that step 4 is a pile of spaghetti waiting to cause havoc ... :-) Cheers, Wol
