Re: [libvirt] RFC backup API

23.03.2016 17:27, John Snow пишет: > > On 03/23/2016 06:36 AM, Kashyap Chamarthy wrote: >> On Mon, Mar 21, 2016 at 01:18:19PM +0300, Maxim Nestratov wrote: >>> Hi all, >>> >>> It's been already quite a long time since qemu implemented QMP >>> "drive-backup" command to create block devices backups. Even more, >>> since qemu 2.4 there is a possibility to create incremental backups. >>> Though it is possible to backup all attached to a domain disk drives >>> by combining them into a single QMP transaction command, this way of >>> creating them, not to mention managing, remains inconvenient for an >>> end user of libvirt. Moreover, creating a single drive backup via QMP >>> interface isn't handy either. That said, it looks reasonable to >>> introduce a *new backup API* based on QMP "drive-backup" facilities. >> There's also the 'blockdev-backup' command, which seems similar in >> operation to 'drive-backup', but differs subtly. >> >> Looking at qmp-commands.hx, I learn that 'blockdev-backup' accepts >> target ID; while 'drive-backup' accept target drive name, otherwise, >> their operation look almost identical, and both commands use >> backup_start() (from qemu/blockdev.c). [Added John Snow in CC to >> correct me if I'm wrong.] >> > No, you're right. Blockdev-backup can backup to an arbitrary device > (which can be backed by a new file), but drive-backup will only accept a > new file. > > I don't think blockdev-backup supports incremental backups just yet, but > I don't think there's any reason it can't. (Looking at it: yeah, why > have I not done that yet?...) John, Any chances to get this implemented? Just not to use two different commands in libvirt and start using 'blockdev-backup' right away for both full and incremental backups?

>> For 'blockdev-backup' >> --------------------- >> >> -> { "execute": "blockdev-backup", "arguments": { "device": "src-id", >> "sync": "full", >> "target": "tgt-id" >> } } >> <- { "return": {} } >> >> >> Where 'tagert' in this case means: >> >> "the name of the backup target device. (json-string)" >> >> >> For 'drive-backup' >> ----------------- >> >> -> { "execute": "drive-backup", "arguments": { "device": "drive0", >> "sync": "full", >> "target": >> "backup.img" } } >> <- { "return": {} } >> >> Here, 'target' means: >> >> "the target of the new image. If the file exists, or if it is a >> device, the existing file/device will be used as the new >> destination. If it does not exist, a new file will be created. >> (json-string)" >> >> [...] >> >> > --js