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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I thought ocfs2 required the disk to be partitioned (super block
corruption).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Has this been fixed ?<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
ocfs2-users-bounces@oss.oracle.com [mailto:ocfs2-users-bounces@oss.oracle.com] <b>On
Behalf Of </b>Luis Freitas<br>
<b>Sent:</b> Friday, July 09, 2010 7:36 AM<br>
<b>To:</b> ocfs2-users@oss.oracle.com<br>
<b>Subject:</b> Re: [Ocfs2-users] partition offset/alignment on SAN devices.<o:p></o:p></span></p>
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<p class=MsoNormal>Thomas and James,<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal> Usually the partition is aligned to the
Cylinder boundary. In the case of a LUN, the cylinder bondary
might have no sense at all? Funny, I never tought about this before.<o:p></o:p></p>
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<p class=MsoNormal> There are some tools that can overwrite a few
sectors on the start of the disk (lilo, grub, DOS fdisk), and expect the
disk to have a partition table, where these sectors are not used for this
reason. <o:p></o:p></p>
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<p class=MsoNormal><br>
I don't know if OCFS2 has provisions for leaving this space
unused.<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>Regards,<o:p></o:p></p>
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<p class=MsoNormal>Luis<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
"Thomas.Zimolong@bmi.bund.de" <Thomas.Zimolong@bmi.bund.de><br>
<b>To:</b> james.masson@tradefair.com; ocfs2-users@oss.oracle.com<br>
<b>Sent:</b> Fri, July 9, 2010 11:24:38 AM<br>
<b>Subject:</b> Re: [Ocfs2-users] partition offset/alignment on SAN devices.<br>
</span><span style='font-size:10.0pt;font-family:"Courier New"'><br>
> mkfs.ocfs2 -L SOMELABEL /dev/dm-10<br>
> This 64k (32/128k whatever) issue is usually only a problem if you've used<br>
a fdisk to create a<br>
> partition to put your data on. For hysterical reasons the first partition<br>
is created an arbitrary<br>
> amount of kb into the disk. This almost never lines up with the LUN<br>
raid-stripe. Then the I/O going<br>
> from app <> FS <> LUN <> disks overlaps block sizes -
causing unnecessary<br>
I/O through the chain and<br>
> sub-optimal performance.<br>
<br>
Hi folks,<br>
<br>
we had that issue too with our CX4-480 and the guys from EMC telling us not<br>
to forget the alignment.<br>
<br>
So we first wondered how to automate this, because we'd have had to align the<br>
partitions on quite a few LUNs (more than 40).<br>
Since you'd have to use the expert options of fdisk, we did'nt find a quick<br>
solution with sfdisk, though with some further investigation there will<br>
surely be one.<br>
<br>
But in the end this was not necessary anyway. We specifically requested that<br>
at EMC and they confirmed, that alignment is only a point when using<br>
partitions at all. We don’t use partitions, so no todo.<br>
<br>
IMHO: Concerning the risk of destroying whatever is on the LUN: If someone<br>
thinks the LUN is unused, just because he/she sees no partition on it, isn't<br>
that more of "a lack of diligence"?<br>
We have a similar situation with ASM-devices: Even if you have a partition on<br>
it, it's not mountable (as there's some ASM data inside it and no FS). So<br>
you'd always have to check more than that to be sure, that the device is<br>
unused.<br>
<br>
Maybe you can clarify that with the vendor of your shared disks.<br>
<br>
Greetings,<br>
Thomas<br>
<br>
_______________________________________________<br>
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<a href="mailto:Ocfs2-users@oss.oracle.com">Ocfs2-users@oss.oracle.com</a><br>
http://oss.oracle.com/mailman/listinfo/ocfs2-users<o:p></o:p></span></p>
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