4 ms·

It doesn't have to stop completely to trigger the problem case, does it? It seems like just being slow enough to trigger the containing system's timeout respons

• zrm 7y ago
  SMR drives shouldn't be that slow. They're slower than PMR drives but it shouldn't be by so much that individual writes are taking tens of seconds. What's probably happening is one of two things. Either the cache gets full and the drive is blocking while it flushes the cache to the disk, or the drive is advertising that it can do a large number of simultaneous write operations which it can't actually do all of in a reasonable amount of time when the cache is full, and then the ones queued last time out. In the first case they could have the firmware continue to process uncached writes when the cache is full, in the second case don't advertise the ability to do as many simultaneous writes. Another alternative might be for the system to use a longer timeout value for these drives, but whether that's reasonable depends on how long it would actually have to be.
  • floatingatoll 7y ago
    This is precisely the origin of my question upstream: Why, precisely, in specific detail, are these rebuilds failing?