Marko Milisavljevic wrote:
Got excited too quickly on one thing... reading single zfs file does
give me almost same speed as dd /dev/dsk... around 78MB/s... however,
creating a 2-drive stripe, still doesn't perform as well as it ought to:
Yes, that makes sense. Because prefetch is disabled, ZFS will only
issue one read i/o at a time (for that stream). This is one of the
reasons prefetch is important :-)
Eg, in your output below you can see that each disk is only busy 40% of
the time when using ZFS with no prefetch:
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
294.3 0.0 37675.6 0.0 0.0 0.4 0.0 1.4 0 40 c3d0
293.0 0.0 37504.9 0.0 0.0 0.4 0.0 1.4 0 40 c3d1
Simultaneous dd on those 2 drives from /dev/dsk runs at 46MB/s per drive.
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
800.4 0.0 44824.6 0.0 0.0 1.8 0.0 2.2 0 99 c3d0
792.1 0.0 44357.9 0.0 0.0 1.8 0.0 2.2 0 98 c3d1
--matt
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