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, by copying the data on the target volume to the destination volume, maintaining changes to data blocks that arise on the target volume during copy operations, copying changed blocks to the destination volume, and repeating changed block updates as necessary until there are no further changed blocks on the target volume (all as more fully described in the specification).
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, wherein said predetermined criteria comprise whether there remain changed blocks in the record created by step (b) after a predetermined time period of processing;
(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, wherein the effect of said command is to simulate a high I/O load on said machine, in order to induce 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. 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, wherein said predetermined criteria comprise whether the number of iterations performed of steps (b) and (c) is greater than one, and the number of changed blocks recorded in the most recent iteration of said step (b) is in excess of a first predetermined number, N, of changed blocks;
(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.
3. The method of claim 2 , wherein N is in the range of 10 to 1000.
4. The method of claim 2 , wherein N is approximately 100.
5. 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, wherein said predetermined criteria comprise whether the number of iterations performed of steps (b) and (c) is in excess of a predetermined number, I, of iterations;
(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.
6. The method of claim 5 , wherein I is approximately 3.