[EMAIL PROTECTED] said: > [b]How the ZFS striped on 7 slices of FC-SATA LUN via NFS worked [u]146 times > faster[/u] than the ZFS on 1 slice of the same LUN via NFS???[/b]
Well, I do have more info to share on this issue, though how it worked faster in that test still remains a mystery. Folks may recall that I said: > Not that I'm not complaining, mind you. I appear to have stumbled across a > way to get NFS over ZFS to work at a reasonable speed, without making changes > to the array (nor resorting to giving ZFS SVN soft partitions instead of > "real" devices). Suboptimal, mind you, but it's workable if our Hitachi > folks don't turn up a way to tweak the array. Unfortunately, I was wrong. I _don't_ know how to make it go fast. While I _have_ been able to reproduce the result on a couple different LUN/slice configurations, I don't know what triggers the "fast" behavior. All I can say for sure is that a little dtrace one-liner that counts sync-cache calls turns up no such calls (for both local ZFS and remote NFS extracts) when things are going fast on a particular filesystem. By comparison, a local ZFS tar-extraction triggers 12 sync-cache calls, and one hits 288 such calls during an NFS extraction before interrupting the run after 30 seconds (est. 1/100th of the way through) when things are working in the "slow" mode. Oh yeah, here's the one-liner (type in the command, run your test in another session, then hit ^C on this one): dtrace -n fbt::ssd_send_scsi_SYNCHRONIZE_CACHE:entry'[EMAIL PROTECTED] = count()}' This is my first ever use of dtrace, so please be gentle with me (:-). [EMAIL PROTECTED] said: > Guess I should go read the ZFS source code (though my 10U3 surely lags the > Opensolaris stuff). I did go read the source code, for my own edification. To reiterate what was said earlier: [EMAIL PROTECTED] said: > The point is that the flushes occur whether or not ZFS turned the caches on > or not (caches might be turned on by some other means outside the visibility > of ZFS). My limited reading of ZFS (on opensolaris.org site) code so far has turned up no obvious way to make ZFS skip the sync-cache call. However my dtrace test, unless it's flawed, shows that on some filesystems, the call is made, and on other filesystems the call is not made. [EMAIL PROTECTED] said: > 2.I never saw the storage controller with cache-per-LUN setting. Cache size > doesn't depend on number of LUNs IMHO, it's a fixed size per controller or > per FC port, SAN-experts-please-fix-me-if-I'm-wrong. Robert has already mentioned array cache being reserved on a per-LUN basis in Symmetrix boxes. Our low-end HDS unit also has cache pre-fetch settings on a per-LUN basis (defaults according to number of disks in RAID-group). Regards, Marion _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
