Request types

blktrace disguingishes between two types of block layer requests, file system and scsi commands. The former are dubbed fs requests, the latter pc requests. File system requests are normal read/write operations, ie any type of read or write from a specific disk location at a given size. These requests typically originate from a user process, but they may also be initiated by the vm flushing dirty data to disk or the file system syncing a super or journal block to disk. pc requests are SCSI commands. blktrace sends the command data block as a payload so that blkparse can decode it.



krzysiek 2007-01-30