[NTLUG:Discuss] Dell Server with PERC RAID

[Cameron, Thomas]

I think I see the difference (and I was not aware of it):

RAID 0+1 is striping data across several disks without parity (benefit of speed), then mirroring that array of disks with an identical set of disks (benefit of fault tolerance).  See http://www.lsilogic.com/products/stor_prod/raid/backgrounder6.html for better details.  I believe this is the more common implementation.

RAID 10 is mirroring disks (benefit of fault tolerance) and then striping data without parity across many volumes comprised of these mirrored disks (benefit of speed).  Look at http://www.lsilogic.com/products/stor_prod/raid/backgrounder7.html for better details.

Thanks for the correction, Chris.  I learned something new today.

Thomas

-----Original Message-----
From: Neil Aggarwal [mailto:neil at JAMMConsulting.com]
Sent: Friday, September 26, 2003 10:30 AM
To: 'NTLUG Discussion List'
Subject: RE: [NTLUG:Discuss] Dell Server with PERC RAID


Chris:

I looked at the referenced articles and I don't see what the 
difference is between RAID 0+1 and RAID 10.

Can you please clarify?

Thanks,
	Neil


--
Neil Aggarwal, JAMM Consulting, (972)612-6056, www.JAMMConsulting.com
FREE! Valuable info on how your business can reduce operating costs by 
17% or more in 6 months or less! => http://newsletter.JAMMConsulting.com

> -----Original Message-----
> From: discuss-bounces at ntlug.org 
> [mailto:discuss-bounces at ntlug.org] On Behalf Of Chris Cox
> Sent: Friday, September 26, 2003 10:08 AM
> To: NTLUG Discussion List
> Subject: Re: [NTLUG:Discuss] Dell Server with PERC RAID
> 
> 
> Cameron, Thomas wrote:
> > RAID 0+1 (often called RAID 10) is two RAID 0 arrays which are
>  > mirrored (RAID 1).  Gives you the benefit of fast striping
>  > plus the fault tolerance of mirroring.  It's just ghastly 
> expensive.
> 
> Actually RAID0+1 and RAID10 are radically different things.
> http://www.acnc.com/04_01_10.html
> http://www.lsilogic.com/products/stor_prod/raid/backgrounder1.html
> 
> Low end RAID controllers do 0+1 (it's easier to handle).  RAID 10 is
> a highly reliable RAID, RAID 0+1 isn't.  You'll only find RAID 10
> on your high end controllers (e.g. a MegaRAID Elite 1600 can do
> RAID 10, perhaps a bit old, but works well with Linux).
> 
> Since disk has become cheap, creation of RAID 10's is now
> quite practical (remember 4G drives used to cost $3000).
> On systems where it works right you get the performance of
> RAID0 with the reliability of RAID1 AND.. unlike RAID0+1,
> you can more than one drive failure (depends on location and
> number of columns though).
> 
> RAID10 is considered the creme de la creme of RAID (but
> probably the most expensive RAID config... but practical
> considering today's disk prices).  You may have to pay
> to get a controller and setup that supports RAID10 though.
> 
> If you need HIGH reliability and FAST reads/writes...
> RAID10 might be a viable choice for you.  Most roll
> the dice and use good quality SCSI and run RAID0+1
> though (mostly because of limitations in their choice
> of RAID controller though).  Or run just RAID1 or
> run RAID5 (slow writes and slow rebuilds).
> 
> The web links above do a pretty good job showing
> the differences between the various RAID levels.
> 
> 
> 
> 
> 
> 
> 
> 
> 
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