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Bug ID 6565574
Synopsis zvol read perf problem
State 10-Fix Delivered (Fix available in build)
Category:Subcategory kernel:zfs
Keywords
Responsible Engineer Neil Perrin
Reported Against
Duplicate Of
Introduced In solaris_nevada
Commit to Fix snv_67
Fixed In snv_67
Release Fixed solaris_nevada(snv_67) , solaris_10u5(s10u5_09) (Bug ID:2156383)
Related Bugs 6560680
Submit Date 5-June-2007
Last Update Date 5-February-2008
Description 
Email from Roch:

I did a quick study for a customer and noticed an
interesting thing. /dev/dsk much slower than /dev/rdsk (for
ZVOL). I now notice that zvol_stategy() issues a
zil_commit() after a dmu_read(). It looks unintended
consequence of

	MrNumber: 6358233
	Synopsis: ZVOL doesn't honour O_DSYNC semantics

root@crazycanucks(31): ptime dd if=/dev/zero of=/dev/zvol/dsk/zfs/vol1 bs=4096 count=1000
1000+0 records in
1000+0 records out

real        2.987
user        0.004
sys         0.129
root@crazycanucks(32): ptime dd if=/dev/zero of=/dev/zvol/rdsk/zfs/vol1 bs=4096 count=1000
1000+0 records in
1000+0 records out

real        0.034
user        0.003
sys         0.029
Work Around 
N/A
Comments 
N/A