Thursday, February 4, 2010

Comparison of Solaris Volume Manager Software & Veritas Volume Manager

Comparison of Solaris Volume Manager Software & Veritas Volume Manager


Sun Microsystems, discourage the use of Veritas on the system disk (root disk/boot disk. Veritas do not, by default, correspond to partitions. In the situation, irrespective of the cause, where the system no longer boots, the sysem administrator must be able to gain access to the file system on the system disk without the drives of the volume management software. This is guaranteed to be possible when each volume corresponds to a partition in the volume tableof contents (VTOC) of the system disk.

Solaris Volume Manager volumes can be accessed even when booted from CD-ROM. This inturn eliminates the need of breaking off a mirrror dring upgrades, thus reducing downtime and complexity of such an operation.

SVM software reservers the correspomdence between the volumes defined in its state database, and the disk partitions defined in the disk lable (VTOC), at all times; disaster recovery is always possible by s standard method, without extra complecations.

It’s easy to grow /var using the VxVM graphical tool. This can be done by anyone at any time, to solve a disk space problem. However, this breaks the volume-partition relation as the /var volume in now a concatenation of two (not necessarily contiguous) sub-disk.

When a disk breaks, the replacement disk is initialized. Slices 3 and 4 become the VxVM private and public region, subdisks are allocated to be mirrored with the surviving disk. Partitions may be created by VxVM software for these subdisks.

There are 2 drawbacks to using SVM software in combinations with VxVM software:

1. Cost
2. SVM software requires that a majority of the state databases be found at boot time (the quorum rule). When all data disks are under VxVM software, only two disks may be left under SVM software. If one of these disks breaks, there is no state database quorum and the system will not boot without manual intervention.

NOTE:
The intervention consists of removing the inaccessible state database copies (using the metadb –d command) and rebooting.

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