[t13] ATA/ATAPI-7 What is Allocation Unit(AU)?

[Hiromichi Oribe]

Does anyone know how to use “Allocation Unit”?  I can’t find anywhere in the ATA/ATAPI-7 document describing how to use this…   Is this just “useful information” for host to know?   Does AU have something to do with Command Completion Time Limit (CCTL) for streaming?   Followings are the only places I can find through out the document.     3.1.11 AU Allocation Unit: The allocation unit is the minimum number of logically contiguous sectors on the media as used in the Streaming feature set. An Allocation Unit may be accessed with one or more requests.   4.17.1.2 Flush to Disk bit The Flush to Disk bit in the WRITE STREAM command specifies that all data for the specified stream shall be flushed to the media before posting command completion. If a host requests flushes at times other than the end of each Allocation Unit, streaming performance may be degraded. The SET FEATURES command to enable/disable caching shall not affect caching for streaming commands.     6.8 CONFIGURE STREAM Sector Count Current - The size of an Allocation Unit in sectors (bits 7:0). Sector Count Previous - The size of an Allocation Unit in sectors (bits 15:8).   Hiromichi Oribe [EMAIL PROTECTED] Iomega Corporation 1821 West Iomega Way, Roy, Utah 84067 tel 801-332-5360 fax 801-332-4667