Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
2001-06-01
2004-08-10
Myers, Paul R. (Department: 2111)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C711S112000, C711S203000, C711S205000
Reexamination Certificate
active
06775790
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a virtual data storage system, and more particularly to a distributed, table-driven virtual storage system having mapping table entries representing virtual storage segments of differing sizes.
BACKGROUND OF THE INVENTION
In a table driven, virtual storage network, a table maps virtual disk segments to physical storage containers. A key issue in forming the virtual networking is the selection of method used to map the virtual storage to the actual storage.
A virtual storage network can map fixed-sized segments of contiguous blocks in each mapping table entry. For mapping efficiency, these segments need to be fairly large, on the order of one megabyte of virtual disk data. One problem with large segments is the time needed to copy large blocks of the underlying non-virtual storage during operations such as the copying or migration of data. During such data movement operations, virtual disk I/O operations to those segments being copied must be stalled until the data movement is finished. This would typically be accomplished by setting a state in the entry to prevent I/O operations to the affected segment. The host write operation cannot be released until the data movement has completed. For large segments, this can add unacceptably long latencies to the virtual disk I/O operation. This delay adversely effects the performance of the storage system by adding undesirably large latencies to virtual disk I/O operations.
The problem of undesirably large latencies during data movement operations can be solved by using smaller segments, but this increases the costs associated with mapping, such as the overhead of storing and managing a much larger number of map entries. This also potentially reduces the amount of contiguous data on the non-virtual storage.
An ideal virtual storage system therefore having a mapping system that achieves the benefits for both large and small segment mapping. In particular, an ideal mapping system would achieve the low administrative cost of larger segmentation and the reduced latencies of smaller segmentation
SUMMARY OF THE INVENTION
In response to these and other needs, the present invention provides a method and system comprising a combination of segment sizes, namely a large segment for the normal case, while breaking the large segment into single disk blocks during data movement. In this way, the administration costs are generally low, but latencies caused by the movement of large data blocks are avoided. The mapping is implemented through distributed mapping agents that may write to the alternative location while the large segment is being moved.
REFERENCES:
patent: 4742447 (1988-05-01), Duvall et al.
patent: 5537534 (1996-07-01), Voigt et al.
patent: 5664187 (1997-09-01), Burkes et al.
patent: 5696934 (1997-12-01), Jacobson et al.
patent: 5778411 (1998-07-01), DeMoss et al.
patent: 5940850 (1999-08-01), Harish et al.
patent: 6038639 (2000-03-01), O'Brien et al.
patent: 6047294 (2000-04-01), Deshayes et al.
patent: 6421767 (2002-07-01), Milillo et al.
patent: 6433787 (2002-08-01), Murphy
patent: 6526478 (2003-02-01), Kirby
patent: 6618798 (2003-09-01), Burton et al.
Montague, Robert M. et al., Virtualizing The SAN, Morgan Keegan & Company, Inc., Jul. 5, 2000, pp. 1-20.
Lary Richard F.
Reuter James M.
Thiel David W.
Hewlett--Packard Development Company, L.P.
Myers Paul R.
Phan Raymond N
LandOfFree
Distributed fine-grained enhancements for distributed table... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Distributed fine-grained enhancements for distributed table..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Distributed fine-grained enhancements for distributed table... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3296982