Features/Livebackup: Difference between revisions
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== Livebackup - A full backup solution for making full and incremental disk backups of a running VM == | == Livebackup - A full backup solution for making full and incremental disk backups of a running VM == | ||
Livebackup provides the ability for an administrator or a management server to use a livebackup_client program to connect to the qemu process and copy the disk blocks that were modified since the last backup was taken. | Livebackup provides the ability for an administrator or a management server to use a livebackup_client program to connect to the qemu process and copy the disk blocks that were modified since the last backup was taken. | ||
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== High Level Design == | == High Level Design == | ||
* When qemu block driver is called to open a virtual disk file, it checks for the presence of a file with suffix .livebackupconf, for example when opening the file vdisk0.img, it would look for a file called vdisk0.img.livebackupconf. | |||
* If the livebackupconf file exists, then this disk is part of the backup set, and the block driver for that virtual disk starts tracking blocks that are modified using an in-memory dirty blocks bitmap. This in-memory dirty blocks bitmap is saved to a file called vdisk0.img.dirty_blocks when the VM shuts down. Thus this dirty blocks bitmap is persisted across VM reboots. It is operated on in memory when the VM is running, but saved to disk when the VM shuts down, and read in again when the VM boots. | |||
* qemu starts a livebackup thread, that listens on a TCP port for connections from livebackup_client | |||
* When the operator wants to take an incremental backup of the running VM, he uses the program livebackup_client. This program opens a TCP connection to the qemu process' livebackup thread. | |||
* First, the livebackup_client issues a snapshot command. | |||
* qemu saves the dirty blocks bitmap of each virtual disk in a snapshot struct, and allocates new in-memory dirty blocks map for each virtual disk | |||
* From now on, till the livebackup_client destroys the snapshot, each write from the VM is checked by the livebackup interposer. If the blocks written are already marked as dirty in the snapshot struct's dirty blocks bitmap, the original blocks are saved off in a COW file before the VM write is allowed to proceed. | |||
to make a snapshot of all the virtual disks of a VM, and then | to make a snapshot of all the virtual disks of a VM, and then | ||
Revision as of 06:18, 27 April 2011
Livebackup - A full backup solution for making full and incremental disk backups of a running VM
Livebackup provides the ability for an administrator or a management server to use a livebackup_client program to connect to the qemu process and copy the disk blocks that were modified since the last backup was taken.
Overview
The goal of this project is to add the ability to do full and incremental disk backups of a running VM. These backups will be transferred over a TCP connection to a backup server, and the virtual disk images will be reconstituted there. This project does not transfer the memory contents of the running VM, or the device states of emulated devices, i.e. livebackup is not VM suspend.
Contact
Jagane Sundar (jagane at sundar dot org)
High Level Design
- When qemu block driver is called to open a virtual disk file, it checks for the presence of a file with suffix .livebackupconf, for example when opening the file vdisk0.img, it would look for a file called vdisk0.img.livebackupconf.
- If the livebackupconf file exists, then this disk is part of the backup set, and the block driver for that virtual disk starts tracking blocks that are modified using an in-memory dirty blocks bitmap. This in-memory dirty blocks bitmap is saved to a file called vdisk0.img.dirty_blocks when the VM shuts down. Thus this dirty blocks bitmap is persisted across VM reboots. It is operated on in memory when the VM is running, but saved to disk when the VM shuts down, and read in again when the VM boots.
- qemu starts a livebackup thread, that listens on a TCP port for connections from livebackup_client
- When the operator wants to take an incremental backup of the running VM, he uses the program livebackup_client. This program opens a TCP connection to the qemu process' livebackup thread.
- First, the livebackup_client issues a snapshot command.
- qemu saves the dirty blocks bitmap of each virtual disk in a snapshot struct, and allocates new in-memory dirty blocks map for each virtual disk
- From now on, till the livebackup_client destroys the snapshot, each write from the VM is checked by the livebackup interposer. If the blocks written are already marked as dirty in the snapshot struct's dirty blocks bitmap, the original blocks are saved off in a COW file before the VM write is allowed to proceed.
to make a snapshot of all the virtual disks of a VM, and then