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The Best Method for Reading, Disk Sectors

Articles and Tips: tip

Michael Spong
Novell, Inc.

01 Jan 2002


Instead of using Media Manager (MM) exclusively to obtain information that is located on the storage media, you can also use Media Manager to locate your hard drive, and use the Object ID to call NPA_HACB_Passthru to have the driver do the job on a more direct level.

Both methods will retrieve your information through the driver, of course, but using NPA_HACB_Passthru will allow you to bypass a few layers (like the CDM) and communicate directly with the HAM. This has several advantages over an exclusively MM approach:

  • It's faster.

  • It allows you to direct specific SCSI commands to the drive, if you want, giving you exclusive control over the hardware, which is something the Media Manager won't allow.

  • You can obtain status information on the devices you communicate with. Media Manager will give you only MM return codes, which have been "best-fit" interpreted from other MM calls. So the MM calls had interpreted the results of the CDM messages, which were interpreted from the original results returned by the HAM.

The NWPA (Novell's storage architecture) specifications, which spec out the NPA_HACB_Passthru call, is located at a link that can be found at the following URL:

http://developer.novell.com/devres/sas/certinfo.htm

* Originally published in Novell AppNotes


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