I've spent some time searching, and I apologize if I've missed this somewhere, but in testing ZVOL write performance I cannot see any noticeable difference between opening a ZVOL with or without O_DSYNC.
Does the O_DSYNC flag have any actual influence on ZVOL writes ? For ZVOLS that I have opened without the O_DSYNC flag, I find that if I follow each write (these are 4KB writes done to a previously written area of a ZVOL) with an fsync() call on the channel, I see a significant performance drop (as expected). But I do not see this behavior when I open the ZVOL with the O_DSYNC flag (and do not do the fsync() operations) as I thought I should. While the O_DSYNC flag is accepted without error when opening a ZVOL it apparently does not support synchronous writes to that ZVOL ... is this correct or am I missing something ? This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
