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List: evms-devel
Subject: RE: Re: [Evms-devel] Feature request: RAID4 without stripping (only
From: "James Lee" <james_lee31 () hotmail ! com>
Date: 2006-02-15 20:24:17
Message-ID: BAY105-W315DCE18AE1E66FDEEC708EFA0 () phx ! gbl
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Yeah, i also think this would be very good functionality to add to the Linux md \
driver (and subsequently to EVMS).
For more information on this, there's a pretty huge thread over at avsforum about \
this: http://www.avsforum.com/avs-vb/showthread.php?t=573986. One of the main guys \
running the company that markets this (limetech) has posted a lot to that thread. I \
posted to it a while back asking if there were any plans GPL the driver code, and \
he's said that it's something they're planning to do that (releasing the driver code, \
but not the management interface). See the following post in the thread: \
http://www.avsforum.com/avs-vb/showthread.php?p=6500421#post6500421.
I don't know what's come of the plans to release this code, but he seems like a \
helpful chap, so it might be worth getting in contact with him. I don't know if Neil \
Brown would be interested in adding this functionality to the kernel?
> Subject: Re: [Evms-devel] Feature request: RAID4 without stripping (only parity)> \
> To: cartman@medsite.info> CC: evms-devel@lists.sourceforge.net> From: \
> steved@us.ibm.com> Date: Wed, 15 Feb 2006 09:34:50 -0600> > Konstantinos Skarlatos \
> wrote on 02/15/2006 07:18:24> AM:> >> -----BEGIN PGP SIGNED MESSAGE----->> Hash: \
> SHA1>>>> Unraid is different from RAID4, because it does no striping. It is just>> \
> a parity drive, that is added in a system of indepependent disks of>> varying \
> capacity and file systems. The data on the data drives are not>> touched by the \
> whole operation, you could add a full drive on the system>> and the only thing that \
> would happen is the recalculation of parity on>> the parity drive. I think Talik \
> described it well:>> [quote]>> Traditional>> RAID 4>> 01 02 03 p>> 04 05 06 p>> 07 \
> 08 09 p>> 10 11 12 p>>>> Traditional>> RAID 5>> 01 02 03 p>> 04 05 p 06>> 07 p 08 \
> 09>> p 10 11 12>>>> UNRAID>> 01 05 09 p>> 02 06 10 p>> 03 07 11 p>> 04 08 12 p>>>> \
> assume the parity bit is always for the horizontal row it's associated> with.>>>> \
> The UNRAID system still uses the data on the other drives as if it was>> striped \
> for purposes of creating the parity disk, the difference is that> the>> data is not \
> actually striped.hope this helps.> > Interesting functionality. The striping in \
> RAID 4 will give you better> throughput since several disks can be accessed at the \
> same time. But if> the disks are fast enough, as you mentioned in a previous post, \
> then> striping won't buy you anything. The Unraid gives you the advantage of> being \
> able to use different sized disks, which is cool. An updated picture> would look \
> like this:> > UNRAID> 01 05 11 p> 02 06 12 p> 03 07 13 p> 04 08 14 p> 09 15 p> 10 \
> p> > The parity disk must therefore be at least as big as the largest data disk.> > \
> RAID 4 requires the same sized disks. If the disks aren't the same size,> it only \
> uses the amount of space on each disk equal to the smallest of the> disks. The rest \
> is wasted.> > I would prefer that this proposed functionality be referred to as \
> "Unraid"> or something other than "RAID 4 without striping". RAID 4 is a technical> \
> specification that includes striping. When I see "RAID 4" I automatically> think of \
> striping. The new RAID layout is not RAID 4. It's more like> concatenation with \
> parity.> > EVMS could add a plug-in for this RAID format, but it won't be useful> \
> without the corresponding code in the kernel. EVMS could provide a patch> to the \
> kernel, but it is best to just have the code in the kernel to begin> with. Anyone \
> up for writing the kernel code and getting it accepted in the> mainline kernel? :)> \
> > Steve D.> > > > -------------------------------------------------------> This \
> > SF.net email is sponsored by: Splunk Inc. Do you grep through log files> for \
> > problems? Stop! Download the new AJAX search engine that makes> searching your \
> > log files as easy as surfing the web. DOWNLOAD SPLUNK!> \
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> > _______________________________________________> Evms-devel mailing list> \
> > Evms-devel@lists.sourceforge.net> To subscribe/unsubscribe, please visit:> \
> > https://lists.sourceforge.net/lists/listinfo/evms-devel
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<body><P >Yeah, i also think this would be very good functionality to add to the \
Linux <FONT class="" >md</FONT> driver (and subsequently to EVMS).</P> <P > </P>
<P >For more information on this, there's a pretty huge thread over at <FONT class="" \
>avsforum</FONT> about this: <A \
> href="http://www.avsforum.com/avs-vb/showthread.php?t=573986" \
> >http://www.avsforum.com/avs-vb/showthread.php?<FONT \
> > class="">t</FONT>=573986</A>. One of the main guys running the company that \
> > markets this (<FONT class="" >limetech</FONT>) has posted a lot to that \
> > thread. I posted to it a while back asking if there were any plans <FONT \
> > class="" >GPL</FONT> the driver code, and he's said that it's something they're \
> > planning to do that (releasing the driver code, but not the management \
> > interface). See the following post in the thread: <A \
> > href="http://www.avsforum.com/avs-vb/showthread.php?p=6500421#post6500421" \
> > >http://www.avsforum.com/avs-vb/showthread.php?p=6500421#post6500421</A>.</P>
<P > </P>
<P >I don't know what's come of the plans to release this code, but he seems like a \
helpful chap, so it might be worth getting in contact with him. I don't know if \
Neil Brown would be interested in adding this functionality to the kernel?<BR ><BR \
></P> <P>
<HR id=stopSpelling>
</P>
<P>> Subject: Re: [Evms-devel] Feature request: RAID4 without stripping (only \
parity)<BR>> To: cartman@medsite.info<BR>> CC: \
evms-devel@lists.sourceforge.net<BR>> From: steved@us.ibm.com<BR>> Date: Wed, \
15 Feb 2006 09:34:50 -0600<BR>> <BR>> Konstantinos Skarlatos wrote on \
02/15/2006 07:18:24<BR>> AM:<BR>> <BR>>> -----BEGIN PGP SIGNED \
MESSAGE-----<BR>>> Hash: SHA1<BR>>><BR>>> Unraid is different from \
RAID4, because it does no striping. It is just<BR>>> a parity drive, that is \
added in a system of indepependent disks of<BR>>> varying capacity and file \
systems. The data on the data drives are not<BR>>> touched by the whole \
operation, you could add a full drive on the system<BR>>> and the only thing \
that would happen is the recalculation of parity on<BR>>> the parity drive. I \
think Talik described it well:<BR>>> [quote]<BR>>> \
Traditional<BR>>> RAID 4<BR>>> 01 02 03 p<BR>>> 04 05 06 \
p<BR>>> 07 08 09 p<BR>>> 10 11 12 p<BR>>><BR>>> \
Traditional<BR>>> RAID 5<BR>>> 01 02 03 p<BR>>> 04 05 p \
06<BR>>> 07 p 08 09<BR>>> p 10 11 12<BR>>><BR>>> \
UNRAID<BR>>> 01 05 09 p<BR>>> 02 06 10 p<BR>>> 03 07 11 \
p<BR>>> 04 08 12 p<BR>>><BR>>> assume the parity bit is always for \
the horizontal row it's associated<BR>> with.<BR>>><BR>>> The UNRAID \
system still uses the data on the other drives as if it was<BR>>> striped for \
purposes of creating the parity disk, the difference is that<BR>> the<BR>>> \
data is not actually striped.hope this helps.<BR>> <BR>> Interesting \
functionality. The striping in RAID 4 will give you better<BR>> throughput since \
several disks can be accessed at the same time. But if<BR>> the disks are fast \
enough, as you mentioned in a previous post, then<BR>> striping won't buy you \
anything. The Unraid gives you the advantage of<BR>> being able to use different \
sized disks, which is cool. An updated picture<BR>> would look like this:<BR>> \
<BR>> UNRAID<BR>> 01 05 11 p<BR>> 02 06 12 p<BR>> 03 07 13 p<BR>> 04 \
08 14 p<BR>> 09 15 p<BR>> 10 p<BR>> <BR>> The parity disk must therefore \
be at least as big as the largest data disk.<BR>> <BR>> RAID 4 requires the \
same sized disks. If the disks aren't the same size,<BR>> it only uses the amount \
of space on each disk equal to the smallest of the<BR>> disks. The rest is \
wasted.<BR>> <BR>> I would prefer that this proposed functionality be referred \
to as "Unraid"<BR>> or something other than "RAID 4 without striping". RAID 4 is a \
technical<BR>> specification that includes striping. When I see "RAID 4" I \
automatically<BR>> think of striping. The new RAID layout is not RAID 4. It's more \
like<BR>> concatenation with parity.<BR>> <BR>> EVMS could add a plug-in for \
this RAID format, but it won't be useful<BR>> without the corresponding code in \
the kernel. EVMS could provide a patch<BR>> to the kernel, but it is best to just \
have the code in the kernel to begin<BR>> with. Anyone up for writing the kernel \
code and getting it accepted in the<BR>> mainline kernel? :)<BR>> <BR>> \
Steve D.<BR>> <BR>> <BR>> <BR>> \
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_______________________________________________<BR>> Evms-devel mailing \
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