Gentlemen, I'm writing to you to ask for your opinion regarding quiescing writes. Here is the situation. In order to take snapshots of all images in a consistency group, we first need to quiesce all the image writers in the consistency group. Let me call group client - a client which requests a consistency group to take a snapshot. Image client - the client that writes to an image. Let's say group client starts sending notify_quiesce to all image clients that write to the images in the group. After quiescing half of the image clients the group client can die. It presents us with a dilemma - what should we do with those quiesced image clients. Option 1 - is to wait till someone manually runs recover for that consistency group. We can show warning next to those unfinished groups when user runs group list command. There will be a command like group recover, which allows users to rollback unsuccessful snapshots or continue them using create snapshot command. Option 2 - is to establish some heart beats between group client and image client. If group client fails to heart beat then image client unquiesces itself and continues normal operation. Option 3 - is to have a timeout for each image client. If group client fails to make a group snapshot within this timeout then we resume our normal operation informing group client of the fact. Which of these options do you prefer? Probably there are other options that I miss. Thanks, Victor. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
