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List:       opensolaris-lvm-discuss
Subject:    Re: [lvm-discuss] SVM root mirroring
From:       "Ian Campbell" <ian () thecampbells ! net>
Date:       2007-05-28 18:20:40
Message-ID: 9e305cf70705281120p7ec6403du63aa5d2b96bc0eee () mail ! gmail ! com
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On 5/26/07, Sanjay Nadkarni <Sanjay.Nadkarni@sun.com> wrote:
>
> Ian Campbell wrote:
> > <snip>
> >
> >
> >     > 7)  In the /etc/system file I add the following two entries at
> >     the end:
> >     > set md:mirrored_root_flag = 1
> >     >
> >     Never!! This is absolutely the wrong thing to do.  You need 3
> metadbs
> >     and preferable on different disks.
> >
> >     </snip>
> >
> >
> > Why should you never do this?  What if your system only has two
> > internal disks?
> The ability to overide the majority quorum was added for a specific
> project which also provided another mechanism to provide an extra vote.
> By setting this flag and not having the additional functionality for the
> extra vote, you risk corruption.    As you point there is a problem with
> only 2 disks.
>
> -Sanjay
>
> >
> >


What was the additional mechanism for the extra vote?

Reality says that we are moving toward smaller profile servers with
limited slots for disk; with root disks being internal and mirrored, we
usually do not have the ability to put replicas on more than two disks.

[Attachment #5 (text/html)]

On 5/26/07, <b class="gmail_sendername">Sanjay Nadkarni</b> &lt;<a \
href="mailto:Sanjay.Nadkarni@sun.com">Sanjay.Nadkarni@sun.com</a>&gt; \
wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" \
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; \
padding-left: 1ex;"> Ian Campbell wrote:<br>&gt; \
&lt;snip&gt;<br>&gt;<br>&gt;<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; &gt; 7)&nbsp;&nbsp;In \
the /etc/system file I add the following two entries \
at<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; the end:<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; &gt; set \
md:mirrored_root_flag = 1<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; &gt; \
<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; Never!! This is absolutely the wrong thing to \
do.&nbsp;&nbsp;You need 3 metadbs<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; and preferable on \
different disks.<br>&gt;<br>&gt;&nbsp;&nbsp;&nbsp;&nbsp; \
&lt;/snip&gt;<br>&gt;<br>&gt;<br>&gt; Why should you never do this?&nbsp;&nbsp;What \
if your system only has two <br>&gt; internal disks?<br>The ability to overide the \
majority quorum was added for a specific<br>project which also provided another \
mechanism to provide an extra vote.<br>By setting this flag and not having the \
additional functionality for the <br>extra vote, you risk \
corruption.&nbsp;&nbsp;&nbsp;&nbsp;As you point there is a problem with<br>only 2 \
disks.<br><br>-Sanjay<br><br>&gt;<br>&gt;</blockquote><div><br>What was the \
additional mechanism for the extra vote?<br><br>Reality says that we are moving \
toward smaller profile servers with  <br>limited slots for disk; with root disks \
being internal and mirrored, we <br>usually do not have the ability to put replicas \
on more than two disks.<br></div></div>



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