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Scalable Metadata for AIX Logical Volume Manager

IP.com Disclosure Number: IPCOM000202155D
Publication Date: 2010-Dec-06
Document File: 1 page(s) / 18K

Publishing Venue

The IP.com Prior Art Database

Abstract

Historically the metadata layout on disk for the AIX (Advanced Interactive Executive) LVM (Logical Volume Manager) does not scale well. For oldvg and bigvg metadata formats the system reserves enough space to accommodate the limit values for maximum logical volumes, maximum physical volumes, and maximum physical partitions. However, it performs I/O to the entire reserved space, even if most of that space is unused. This does more I/O than necessary, because there is no concept of an intermediate configuration. For oldvg and bigvg metadata formats, the drawback is not obvious, because those have rather small limit values. However, if this trend were to continue into the svg (scalable volume group) metadata format the performance degradation would be obvious for even the smallest svg configurations.

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Scalable Metadata for AIX Logical Volume Manager

Historically the metadata layout on disk for the AIX® (Advanced Interactive Executive) LVM (Logical Volume Manager) does not scale well. For oldvg and bigvg metadata formats the system reserves enough space to accommodate the limit values for maximum logical volumes, maximum physical volumes, and maximum physical partitions. However, it performs I/O to the entire reserved space, even if most of that space is unused. This does more I/O than necessary, because there is no concept of an intermediate configuration. For oldvg and bigvg metadata formats, the drawback is not obvious, because those have rather small limit values. However, if this trend were to continue into the svg (scalable volume group) metadata format the performance degradation would be obvious for even the smallest svg configurations.

Scalable volume group metadata format reserves enough space to accommodate its architectural limit, but unless an administrator is taking advantage of those limits they do not have to enter a configuration where I/O is performed to the entire reserved area. The scalable volume group metadata format offers intermediate limit values for maximum logical volumes and maximum physical partitions. These intermediate values step gradually towards the architectural limit, and I/O is only performed up to the intermediate limit value.

For each of the metadata formats, there is a structure known as the lvm record located at a know...