NAME

       blkreplay - block device testing and benchmarking tool

SYNOPSIS

       blkreplay [options] device

DESCRIPTION

       blkreplay is a utility driving the block layer of the operating system while measuring
       latency and throughput of I/O operations for later visualisation.

       blkreplay can create artificial loads (random read-write sweeps, various kinds of overload
       tests) or replay natural loads which have been recorded by blktrace or a similar utility
       run at production servers.

       blkreplay can be used to test physical hardware, to compare different brands of hard disks
       or RAID controllers, to evaluate the effect of SSD caching, to compare different block
       level transports like iSCSI vs Fibrechannel and so on.

       blkreplay parses the load data from stdin. To create load data from blktrace output, use
       conv_blktrace_to_load.sh script.

OPTIONS

       Influence replay duration:
           --replay-start=val
               start offset (in seconds, 0=from_start)

           --replay-end=val
               end offset (in seconds, 0=unlimited)

           --replay-duration=val
               alternatively specify the end offset as delta

           --replay-out=val
               start offset, used for output (in seconds)

           --start-grace=val
               start after grace period for filling the pipes (in seconds)

       Handling of conflicting I/O requests:
           --with-conflicts
               conflicting writes are ALLOWED (damaged I/O)

           --with-drop
               conflicting writes are simply dropped

           --with-partial
               partial ordering by pushing back conflicts (default)

           --with-ordering
               enforce total order in case of conflicts

           --strong=val
               mode between 0 and 2, see docs (default=1)

       Replay parameters:
           --threads=val
               parallelism (default=1024)

           --fill-random=val
               fill data blocks with random bytes (%, default=0)

       Verification modes:
           --no-overhead
               verify is OFF (default)

           --with-verify
               verify on reads

           --with-final-verify
               additional verify pass at the end

           --with-paranoia
               re-read after each write (destroys performance)

       Convenience:
           --verbose=val
               increase verbosity, show additional INFO: output

       Expert options (DANGEROUS):
           --o-direct
               use O_DIRECT (default)

           --no-o-direct
               don't use O_DIRECT, deliver FAKE results

           --o-sync
               use O_SYNC

           --no-o-sync
               don't use O_SYNC (default)

           --dry-run
               don't actually do I/O, measure internal overhead

           --fake-io
               omit lseek() and tags, even less internal overhead

           --simulate-io=val
               delay value for I/O simulation (timespec sec.nsec)

           --ahead-limit=val
               limit pipe fillahead (realtime sec.nsec)

           --fan-out=val
               only for kernel hackers (default=4)

           --no-dispatcher
               only for kernel hackers

           --bottleneck=val
               max #requests on dispatch

           --speedup=val
               speedup / slowdown by REAL factor (default=1.0)

           --mmap-mode
               use mmap() instead of read() / write() [NYI]

AUTHORS

       blkreplay was written by Thomas Schoebel-Theuer. This manual page was created from
       blkreplay documentation by Andrew Shadura.

COPYRIGHT

       Copyright 2009-2012 Thomas Schoebel-Theuer

SEE ALSO

       blktrace(8)

                                            2021-01-06                               BLKREPLAY(1)