VERITAS Storage Foundation 4.1 Oracle Administrator's Guide

Chapter 1, VERITAS Storage Foundation for Oracle

Prerelease 8 September 2005, 8:54am VERITAS Volume Manager

Persistent FastResync

Non-persistent FastResync has been augmented by the introduction of persistent FastResync.

Unlike non-persistent FastResync, Persistent FastResync keeps the FastResync maps on disk so

that they can survive system reboots and system crashes. When the disk groups are rejoined, this

allows the snapshot plexes to be quickly resynchronized. This ability is not supported by

non-persistent FastResync.

If persistent FastResync is enabled on a volume or on a snapshot volume, a DCO and a DCO log

volume are associated with the volume.

In VxVM 3.2 and 3.5, the DCO object only managed information about the FastResync maps.

These maps track writes to the original volume (and to each of up to 32 snapshot volumes) since the

last snapshot operation. The DCO log volume on disk holds the 33 maps, each of which is 4

blocks in size by default.

In VxVM 4.1, the DCO object is used not only to manage FastResync maps, but also to manage

DRL recovery maps and special maps called copy maps that allow instant snapshot operations to be

resume following a system crash.

Persistent FastResync can also track the association between volumes and their snapshot

volumes after they are moved into different disk groups. When the disk groups are rejoined, this

allows the snapshot plexes to be quickly resynchronized. This ability is not supported by

non-persistent FastResync.

Disk Group Split and Join (Optional)

Disk group split and join is included with the Enterprise Edition. It is also included as part of the

VERITAS FlashSnap option with the Standard Edition.

VxVM provides a disk group content reorganization feature that supports general disk group

reorganization and allows you to move volume snapshots to another host for off-host backup.

Additional options to the vxdg command enable you to take advantage of the ability to remove all

VxVM objects from an imported disk group and move them to a newly created target disk group

(split), and to remove all VxVM objects from an imported disk group and move them to an

imported target disk group (join). The move operation enables you to move a self-contained set

of VxVM objects between the imported disk groups.

Hot-Relocation

In addition to providing volume layouts that help improve database performance and availability,

VxVM offers features that you can use to further improve system availability in the event of a disk

failure. Hot-relocation is a feature that allows a system to react automatically to I/O failures on

mirrored or RAID-5 volumes and restore redundancy and access to those volumes.