On 08/09/2015 10:00, Denis V. Lunev wrote:
How the given solution works?
If disk-deadlines option is enabled for a drive, one controls time completion
of this drive's requests. The method is as follows (further assume that this
option is enabled).
Every drive has its own red-black tree for keeping its requests.
Expiration time of the request is a key, cookie (as id of request) is an
appropriate node. Assume that every requests has 8 seconds to be completed.
If request was not accomplished in time for some reasons (server crash or smth
else), timer of this drive is fired and an appropriate callback requests to
stop Virtial Machine (VM).
VM remains stopped until all requests from the disk which caused VM's stopping
are completed. Furthermore, if there is another disks with 'disk-deadlines=on'
whose requests are waiting to be completed, do not start VM : wait completion
of all "late" requests from all disks.
Furthermore, all requests which caused VM stopping (or those that just were not
completed in time) could be printed using "info disk-deadlines" qemu monitor
option as follows:
This topic has come up several times in the past.
I agree that the current behavior is not great, but I am not sure that
timeouts are safe. For example, how is disk-deadlines=on different from
NFS soft mounts?