Method for creating consistent backup image of a storage volume without requiring a snapshot
View Patent ↗Method for creating a consistent image, on a destination volume, of a target volume that remains in production use while the image is being created, without requiring the use of a snapshot.
1. A method for creating a consistent image of a target volume under control of an operating system running on a machine, said target volume comprising a plurality of data blocks, wherein said target volume remains available for read and write operations during the period that such consistent image is being created, said method comprising:
(a) copying all of the data in the target volume to a destination volume without regard to changes in the data while it was being copied;
(b) maintaining a record identifying those data blocks on the target volume that have changed since the beginning of the most recent prior step (a) or step (c);
(c) copying to the destination volume those data blocks identified by said record as having changed on the target volume since the beginning of the most recent prior step (a) or step (c), in such manner as to replace any prior representation of those blocks on the destination volume;
(d) determining whether said consistent image is sufficiently stabilizing, in accordance with predetermined criteria, in light of processing loads experienced during the image creation process;
(e) if said consistent image is determined not to be sufficiently stabilizing, issuing a command to said operating system to slow down the processing of I/O queues on said machine; and
(f) repeating steps (b) and (c) until said record shows no changed blocks on the target volume.
2. The method of claim 1 , wherein said record is a bitmap.
3. The method of claim 1 , wherein said replacing prior representations comprises overwriting said prior representations.
4. The method of claim 1 , wherein said target volume is a single partition on a hard disk.
5. The method of claim 1 , wherein said target volume is a logical volume comprising a plurality of other storage volumes.
6. The method of claim 1 , wherein said predetermined criteria comprise whether there remain changed blocks in the record created by step (b) after a predetermined time period of processing.
7. The method of claim 6 , further comprising issuing a further command to said operating system to further slow down the processing of I/O queues on said machine if there remain changed blocks in the record created by step (b) after a further predetermined time period of processing.
8. The method of claim 6 , further comprising issuing a further command to said operating system to suspend the processing of I/O queues on said machine if there remain changed blocks in the record created by step (b) after a further predetermined time period of processing.
9. The method of claim 1 , wherein said operating system is Linux and said command comprises a set queue congested call.
10. The method of claim 1 , wherein said slowing down the processing of I/O queues comprises temporarily stopping said processing.
11. The method of claim 10 , wherein said operating system is Windows and said command comprises an IOCTL_VOLSNAP_FLUSH_AND_HOLD_WRITES call.