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