As it turns out, I did a little rgreping in the source and it seems like I found a way to disable disk-barrier and disk-flushes in drbd 8.4.1.<div><br></div><div>In drbd/drbd_receiver.c, the write ordering method seems like it's determined in the drbd_bump_write_ordering function. Inside the idr_for_each_entry loop I hard coded wo = WO_drain_io.</div>
<div><br></div><div>I compiled the kernel module and tested it and it showed 'wo:d' like it should. As predicted the dd latency test went way down, but so did the throughput test. I think I'll probably just stick with barrier and take the latency hit, but I thought I'd post this in case anyone else wants to fool around with this setting.</div>
<div><br></div><div>Chris<br><br><div class="gmail_quote">On Mon, Apr 2, 2012 at 7:55 AM, Chris Dickson <span dir="ltr"><<a href="mailto:chrisd1100@gmail.com">chrisd1100@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Interesting, I'm starting to think that a lot of these performance issues people are seeing with 8.4.1 are related to this feature. I remember when tweaking in 8.3 turning off flushes improved latency dramatically.<div>
<br></div><div>I wonder if there is a patch for the source out there? Maybe I'll consult the dev list to locate the spot in the code where this decision gets made and hard code turning off barrier and flushes.<div><div class="h5">
<br><br>
<div class="gmail_quote">On Mon, Apr 2, 2012 at 2:26 AM, Christian Balzer <span dir="ltr"><<a href="mailto:chibi@gol.com" target="_blank">chibi@gol.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Hello,<br>
<div><div><br>
On Sat, 31 Mar 2012 11:42:33 -0400 Chris Dickson wrote:<br>
<br>
> It seems that ever since I upgraded to drbd 8.4.1 the 'disk-barrier no;'<br>
> and 'disk-flushes no;' options are not being respected in my resource<br>
> configuration file. A 'cat /proc/drbd' shows 'wo:b' regardless of what<br>
> options I set in the resource config. I also tried to set these via the<br>
> command line with drbdsetup to no avail.<br>
><br>
> Anyone else seeing this issue and are there any known workarounds?<br>
><br>
</div></div>I can confirm that. Saw the same thing setting up my latest DRBD cluster<br>
here and promptly moved to 8.3.12, which fixed this and a slew of other<br>
problems and performance issues.<br>
<br>
Regards,<br>
<br>
Christian<br>
<span><font color="#888888">--<br>
Christian Balzer Network/Systems Engineer<br>
<a href="mailto:chibi@gol.com" target="_blank">chibi@gol.com</a> Global OnLine Japan/Fusion Communications<br>
<a href="http://www.gol.com/" target="_blank">http://www.gol.com/</a><br>
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</blockquote></div><br></div>