Re: raid10 vs raid01 type in dmraid

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On Thu, Jun 21, 2007 at 09:23:32AM -0700, Gaston, Jason D wrote:
> >-----Original Message-----
> >From: Heinz Mauelshagen [mailto:mauelshagen@xxxxxxxxxx] 
> >Sent: Thursday, June 21, 2007 3:38 AM
> >To: Gaston, Jason D
> >Cc: mauelshagen@xxxxxxxxxx; ATARAID (eg, Promise Fasttrak, 
> >Highpoint 370) related discussions
> >Subject: Re: raid10 vs raid01 type in dmraid
> >
> >On Tue, Jun 19, 2007 at 03:52:14PM -0700, Gaston, Jason D wrote:
> >> I think that the array for nested raid levels, in metadata.c, may be
> >> upside down.  When I build a raid0+1 with Intel or Nvidia (one mirror
> >> array of two stripe arrays), it is reported as a "raid10" 
> >with [dmraid
> >> -s], this should be "raid01".  If I reverse the nesting to raid10, in
> >> Intel (one stripe array of two mirror arrays), it is reported as a
> >> "raid01" with [dmraid -s], this should be "raid10".
> >> 
> >> Can we just reverse the array in metadata.c?
> >
> >Nope, this is a question of the definition of RAID10 and 
> >RAID01 (or RAID0+1).
> >
> >I use RAID10 for a mirror on top of 2 (or more) striped sets vs.
> >RAID01 for a stripe on top of 2 (or more) mirror sets in dmraid.
> >
> >Ie. looking at the device stack from the top to the bottom.
> >
> >So the example you made above (Intel or NVidia) with one mirror of
> >2 striped arrays is a RAID10 by that definition.
> >
> >Heinz
> >
> >> 
> >> From:
> >> static const char *stacked_ascii_type[][5] = {
> >> 	{ "raid10", "raid30", "raid40", "raid50", "raid60" },
> >> 	{ "raid01", "raid03", "raid04", "raid05", "raid06" },
> >> };
> >> 
> >> To:
> >> static const char *stacked_ascii_type[][5] = {
> >> { "raid01", "raid03", "raid04", "raid05", "raid06" },	
> >> { "raid10", "raid30", "raid40", "raid50", "raid60" },
> >> 	
> >> }; 
> >> 
> >> Thanks,
> >> 
> >> Jason
> >
> 
> 
> Where did we get that definition for RAID10 from?  Everywhere that I
> look I see the reverse definition for RAID10 vs RAID 0+1.  Nvidia even
> defines their RAID as 0+1 in their OROM and MediaShield documentation.

Eg, PC Magazine:
"RAID 10, RAID 100 - Speed and Fault Tolerance
RAID 10 is RAID 1 + 0. The drives are striped for performance (RAID 0), and all striped drives are duplicated (RAID 1) for fault tolerance."

Yes, I konw, there's different (aargh!) definitions out there.

Like I said: the top -> bottom of the stack definition is preferable
to me (you reach the mirror first and the stripe second while walking
the stack from the top to the bottom).

We just got to hold on to one definition in dmraid,

Heinz

> 
> Thanks,
> 
> Jason

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