On Jun 8, 2010, at 12:46 PM, Miles Nordin wrote: >>>>>> "re" == Richard Elling <richard.ell...@gmail.com> writes: > > re> Please don't confuse Ethernet with IP. > > okay, but I'm not. seriously, if you'll look into it.
[fine whine elided] I think we can agree that the perfect network has yet to be invented :-) Meanwhile, 6Gbps SAS switches are starting to hit the market... what fun :-) > re> The latest OpenSolaris release is 2009.06 which treats all > re> Zvol-backed COMSTAR iSCSI writes as sync. This was changed in > re> the developer releases in summer 2009, b114. For a release > re> such as NexentaStor 3.0.2, which is based on b140 (+/-), the > re> initiator's write cache enable/disable request is respected, > re> by default. > > that helps a little, but it's far from a full enough picture to be > useful to anyone IMHO. In fact it's pretty close to ``it varies and > is confusing'' which I already knew: > > * how do I control the write cache from the initiator? though I > think I already know the answer: ``it depends on which initiator,'' > and ``oh, you're using that one? well i don't know how to do it > with THAT initiator'' == YOU DON'T For ZFS over a Solaris initiator, it is done with setting DKIOCSETWCE via an ioctl. Look on or near http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/vdev_disk.c#276 I presume that this can also be set with format -e, as is done for other devices. Has anyone else tried? > > * when the setting has been controlled, how long does it persist? > Where can it be inspected? RTFM stmfadm(1m) and look for "wcd" <small_rant> drives me nuts that some people prefer negatives (disables) over positives (enables) </small_rant> > > * ``by default'' == there is a way to make it not respect the > initiator's setting, and through a target shell command cause it to > use one setting or the other, persistently? See above. > * is the behavior different for file-backed LUN's than zvol's? Yes, it can be. It can also be modified by the sync property. See CR 6794730, need zvol support for DKIOCSETWCE and friends http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6794730 > I guess there is less point to figuring this out until the behavior is > settled. I think it is settled, but perhaps not well documented :-( -- richard -- ZFS and NexentaStor training, Rotterdam, July 13-15, 2010 http://nexenta-rotterdam.eventbrite.com/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
