From 0228cfe7bb04b3c8329f8e77ee47e30e1a5a03cd Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 18 Oct 2016 09:12:45 -0600 Subject: [PATCH 1/1] HOWTO: update to include iolog replay Signed-off-by: Jens Axboe --- HOWTO | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/HOWTO b/HOWTO index cf1024cf..3f8acee1 100644 --- a/HOWTO +++ b/HOWTO @@ -1558,10 +1558,10 @@ read_iolog=str Open an iolog with the specified file name and replay the replay_no_stall=int When replaying I/O with read_iolog the default behavior is to attempt to respect the time stamps within the log and - replay them with the appropriate delay between IOPS. By + replay them with the appropriate delay between IOPS. By setting this variable fio will not respect the timestamps and attempt to replay them as fast as possible while still - respecting ordering. The result is the same I/O pattern to a + respecting ordering. The result is the same I/O pattern to a given device, but different timings. replay_redirect=str While replaying I/O patterns using read_iolog the @@ -1573,13 +1573,14 @@ replay_redirect=str While replaying I/O patterns using read_iolog the mapping. Replay_redirect causes all IOPS to be replayed onto the single specified device regardless of the device it was recorded from. i.e. replay_redirect=/dev/sdc would cause all - IO in the blktrace to be replayed onto /dev/sdc. This means - multiple devices will be replayed onto a single, if the trace - contains multiple devices. If you want multiple devices to be - replayed concurrently to multiple redirected devices you must - blkparse your trace into separate traces and replay them with - independent fio invocations. Unfortuantely this also breaks - the strict time ordering between multiple device accesses. + IO in the blktrace or iolog to be replayed onto /dev/sdc. + This means multiple devices will be replayed onto a single + device, if the trace contains multiple devices. If you want + multiple devices to be replayed concurrently to multiple + redirected devices you must blkparse your trace into separate + traces and replay them with independent fio invocations. + Unfortuantely this also breaks the strict time ordering + between multiple device accesses. replay_align=int Force alignment of IO offsets and lengths in a trace to this power of 2 value. -- 2.25.1