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<div class="gmail_quote">On Sat, Mar 15, 2014 at 9:54 AM, Jason
Keltz<span class="Apple-converted-space"> </span><span dir="ltr"><<a
rel="nofollow" href="mailto:jas%20cse%20yorku%20ca"
target="_blank">jas cse yorku ca</a>></span><span
class="Apple-converted-space"> </span>wrote:<br>
<blockquote class="gmail_quote" style="margin: 0px 0px 0px
0.8ex; border-left-width: 1px; border-left-color: rgb(204,
204, 204); border-left-style: solid; padding-left: 1ex;">Hi
everyone..<br>
I've seen a lot of conflicting information with respect to
support of write barriers on MD and LVM devices under RHEL6.
I'm surprised that this question hasn't come up on this list
before! I'm building a system with MD RAID10, and putting LVM
on top of it, using ext4 filesystems. I'd like to know
whether write barriers are supported through the complete
chain in this environment. When I mount the filesystems,
there are no kernel errors that barriers are not supported,
but I don't want to be under the false impression that
barriers "appear" to be supported, yet are not. For example,
I've read that barriers were only supported on MD at all
levels in 2.6.33 (previously only RAID1). While RHEL6 is based
on 2.6.32, I "assume" that RH would backport an important
change like that, or, at least have a warning in the
documentation, but I can't find any mention of this. I've
also read quite mixed messages about barrier support in LVM as
well. Any help would be much appreciated.<br>
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<br>
Hi,<br>
<br>
I've searched for a solid answer to this question myself but so far
I'm still in the dark. Can anyone categorically state for the record
(or point to some clear documentation) whether or not write barrier
support is indeed implemented for LVM under RHEL 6?<br>
<br>
My expectation is that LVM write barrier support will have been
back-ported to the current 2.6.32 RHEL kernel. I've googled until my
fingers and eyes are sore but I can't find anything to support that
assumption. I looked here, too:<br>
<br>
<a class="moz-txt-link-freetext" href="https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.5_Technical_Notes/index.html">https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html-single/6.5_Technical_Notes/index.html</a><br>
<br>
But it's inconclusive as to the support for write barriers in LVM.<br>
<br>
Help please. Anyone?<br>
<br>
Kind regards,<br>
Tom<br>
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<pre class="moz-signature" cols="100">--
Tom Robinson
IT Manager/System Administrator
MoTeC Pty Ltd
121 Merrindale Drive
Croydon South
3136 Victoria
Australia
T: +61 3 9761 5050
F: +61 3 9761 5051
E: <a class="moz-txt-link-abbreviated" href="mailto:tom.robinson@motec.com.au">tom.robinson@motec.com.au</a>
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