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Conclusion
While the examples in this article use Sun StorEdge Instant Image software and Sun Solstice Backup software, it is possible to obtain similar results with other backup tools such as Veritas Netbackup.
Veritas Netbackup also includes a snapshot option called FlashBackup. FlashBackup uses a dependent copy (or copy-on-write). Although this feature is an interesting way of obtaining a PIT copy (because it can be created quickly), it does not relieve the I/O on the master volume, and therefore the backup degrades performance of applications using this volume.
The PIT method described in this article is particularly applicable if the volume backed up is a UFS type file system. The main reason is that a snapshot is successful if the master volume can be quiesced during creation of the shadow volume. In our examples, we used the command lockfs to achieve this. This is not applicable for raw partitions, however. For raw partitions, other processes must be developed to make sure nothing is written on the volume (unmounting it, stopping all applications using it, and so on).
In conclusion, with a small investment in backup planning and configuration, you can implement backup strategies that effectively shorten the backup window, thus improving the availability of important applications such as databases, web servers, and home directories.