<br><font size=2 face="sans-serif">External metadata brings some advantages
over internal metadata, especialy when it comes to resizing as well as
recovery. If you want to maximize speed for metadata you could use a ssd
connected to a dedicated controller. Given the small diskspace needed for
metadata and the rather low price of such ssd nowadays this is probably
the best solution. if you want to migrate existing partitions to DRBD external
metadata AFAIK is the only way to do it<br>
</font><font size=2 color=#5f5f5f face="sans-serif">Mit freundlichen Grüßen
/ Best Regards<b><br>
</b><br>
Robert Köppl</font>
<br><font size=2 color=#5f5f5f face="sans-serif"><br>
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Fax: +43 3842 82930-500<br>
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<td width=40%><font size=1 face="sans-serif"><b>Mark Morlino <mrmorlino@alaska.edu></b>
</font>
<br><font size=1 face="sans-serif">Gesendet von: drbd-user-bounces@lists.linbit.com</font>
<p><font size=1 face="sans-serif">14.01.2011 08:40</font>
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<div align=right><font size=1 face="sans-serif">An</font></div>
<td><font size=1 face="sans-serif">drbd-user@lists.linbit.com</font>
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<div align=right><font size=1 face="sans-serif">Kopie</font></div>
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<div align=right><font size=1 face="sans-serif">Thema</font></div>
<td><font size=1 face="sans-serif">Re: [DRBD-user] difference in speed
when using external metadata</font></table>
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<br><tt><font size=2>On Mon, Jan 10, 2011 at 10:31 AM, Bart Coninckx<br>
<bart.coninckx@telenet.be> wrote:<br>
> On Monday 10 January 2011 19:40:17 J. Ryan Earl wrote:<br>
>> On Sun, Jan 9, 2011 at 10:03 AM, Bart Coninckx<br>
> <bart.coninckx@telenet.be>wrote:<br>
>> > Hi all,<br>
>> ><br>
>> > am reading the Novell docs on DRBD and one of the ways they
mention to<br>
>> > speed<br>
>> > up DRBD is using external metadata. Possibly a hard question
to answer<br>
>> > but could someone indicate by what degree this would enhance
speed<br>
>> > (provided using<br>
>> > a sufficient fast disk for the metadata, like a SSD)?<br>
>> ><br>
>> > thx!<br>
>> ><br>
>> > Bart<br>
>><br>
>> A RAID controller with a backed-write cache essentially nullifies<br>
>> any advantage there. A RAID controller that can instantly
return on<br>
>> FUA-writes is what you want.<br>
>> -JR<br>
><br>
> Hi,<br>
><br>
> so the essence of your answer is that this is not a matter of having
metadata<br>
> internal or external, but rather of having the right RAID controller?<br>
> Do you have examples of these in the major brands (HP, Dell, ...)
?<br>
><br>
> thx!<br>
><br>
><br>
><br>
> B.<br>
> _______________________________________________<br>
> drbd-user mailing list<br>
> drbd-user@lists.linbit.com<br>
> http://lists.linbit.com/mailman/listinfo/drbd-user<br>
><br>
<br>
I would be interested in this information too (in my case I'd be<br>
interested in any supermicro controllers that meet this requirement).<br>
If I understand correctly, an FUA-write is a write-through request.<br>
Doesn't that mean that the controller should not return until<br>
everything has been physically written to the disk? It seems to me<br>
that in order to return instantly on an FUA-write, the controller<br>
would have to ignore the FUA request and return once the data has been<br>
written to the cache. I don't see how it can both force physical disk<br>
access and return instantly. Perhaps I'm missing something, it<br>
certainly wouldn't be the first time.<br>
<br>
-Mark<br>
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