restore log pubs from tapebackup with file = 2, recovery, stopat ‘Dec 29, 1999 2:30PM’

Backup media and hardware

Selecting the appropriate backup media for yrou environment can have a large impact on how much data you can backup and the amount of time a restore will take. In a nutshell, selecting backup devices and media is relatively simple. You want to purchase the largest and fastest device as your budget will allow. You might think that is a dumb statement, but I’ve been in many companies where backups took an excessive amount of time or were almost impossible simply because the company was not willing to spend an extra $1000 dollars or so for a much more appropriate solution.

The most common backup media is tape. Tape comes in many different varieties, but DAT and DLT are the most common with DLT now being the most popular choice.

DAT tapes can generally store 4GB uncompressed and 8GB compressed. This is adequate storage for many databases. However in many enviironment nowadays, it can require two or more tapes in order to perform full database backups on an entire server. This forces the DBA to either schedule backups during the day when they can change tapes, have a night operator switch tapes, or stagger backups across days so that only portions of the server get full backups each day. This introduces a level of error, increases the complexity of a restoration, and negatively impacts the production environment. Additionally, many server have databases that are interdependent. Using staggered backkups can introduce inconsistencies in the data since it might not be possible to fit all of the interdependent databases into a single backup. The other limiting factor is speed. DAT drives are very slow in comparison to any other backup solution. It will normally take several hours to backup 4GB of data.

Due to the limitations of DAT, many companies are switching to DLT and it has become the media of choice in the majority of companies. It is almost exclusively specified for any new system. DLT dramatically increases storage capacity. Currently, DLT comes in two popular capacities: 15GB/30GB and 35GB/70GB. This increased capacity now gives administrators the capacity needed to keep backup sets together. By far the most popular is the 35GB/70GB. This offers enough capacity for the majority of installations to backup and entire server to a single tape. Additionally, the speed is significantly greater. You can normally fill a DLT tape to capacity in less time than it would take to fill the much smaller DAT tapes. So not only does DLT hold more data on a single tape, it is orders of magnitude faster than DAT.

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