Best Practices for drive cleaning.

Article:TECH8306  |  Created: 2000-01-05  |  Updated: 2013-10-24  |  Article URL
Article Type
Technical Solution



Best Practices for drive cleaning.


There are three ways to accomplish tape cleaning.
I. Frequency based cleaning
II. Robotic cleaning
III. TapeAlert

I. Frequency based cleaning can be implemented in NetBackup by tracking the time the drive has been in use, and when the drive reaches a configurable parameter, NetBackup essentially creates a job that mounts and exercises a cleaning tape. This cleans the drive in a preventive fashion. The advantage is that typically there aren't any drives unavailable awaiting cleaning. There is also no limitation on platform or robot specifications, it works with everything. On the downside, cleaning is done more often than is really necessary. This adds system wear and eats up time that could be used to write to the drive. Another limitation is that it is hard to tune. Some new tapes are "dirty," but generally speaking, as the tape inventory ages the need for cleaning increases. This increases the amount of tuning administration needed and consequently the margin of error. Frequency based cleaning was available in NetBackup 3.1.1 and is still available in 3.4. Frequency based cleaning is not possible with Shared Storage Option (SSO), as there is no single device path where mounts can be accurately counted.

II. Robotic cleaning is not proactive, and is not subject to the limitations detailed above. By being reactive, unnecessary cleanings are eliminated, frequency tuning is not an issue, and the drive can spend more time moving data, rather than in maintenance operations. The flaw in the solution is that every vendor has implemented it in a different way. A limitation here is that not all OS's or even OS versions handle robotic cleaning in the same reliable fashion, due to being so new. Robotic cleaning may have functioned at some level with some OS's and versions. Such behavior was seen with Solaris 2.51 and NetBackup 3.1.1, but was not supported, despite the fact it may have functioned. While this option may continue to function for some configurations (most notably those that do not support TapeAlert such as IBM) it is not supported.

III. TapeAlert This feature allows reactive cleaning for most drive types. TapeAlert allows a tape drive to notify Media Manager when it needs to be cleaned. Media Manager then performs the cleaning. You must have a cleaning tape configured for the robot in order to utilize this feature. TapeAlert is the recommended cleaning solution if it can be implemented.

Not all platforms, robots, and drives, at all firmware levels, support this type of reactive cleaning. In the case where reactive cleaning is not supported on a particular drive, frequency-based cleaning may be utilized. This solution is not vendor or platform specific. TapeAlert was not supported in NetBackup 3.1.1, but since NetBackup 3.2 it has been supported. The specific firmware levels have not been tested by VERITAS, however the vendor should be able to confirm that the TapeAlert feature is supported.

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