RE: Questions about VERY large software raid config

Isn't it 2TB per RAID device (i.e. Linux block device) or 2TB in total?


I have 28 36GB 15K drives and 28 18GB 15K drives.

36GB * 28 = 1008GB
18GB * 28 = 504GB

Either way, that's below the 2TB limit.  However, since I'm mirroring,
it will effectively be ~750GB.  

But I would like to know if there is a 2TB *total* limit for ALL RAID
devices (good information to know in advance :) ).

I'm going to be running LVM on top of the resulting md device for
snapshots as well.  I have a Red Hat kernel (2.4.18-24) so I assume that
the vfs-lock patch is already integrated since Red Hat offers LVM as an
option in 7.3.  I've tested snapshots on my small setup and it appears
to work just fine with ext3 on LVM on software RAID.

Thanks for the help,
Andy.  

-----Original Message-----
From: Mike Dresser [mailto:mdresser_l@windsormachine.com] 
Sent: Friday, February 21, 2003 10:50 AM
To: Rechenberg, Andrew
Cc: linux-raid@vger.kernel.org
Subject: Re: Questions about VERY large software raid config


On Fri, 21 Feb 2003, Rechenberg, Andrew wrote:

Basically I'm going to do a bunch of RAID1 mirrors (56 drives), RAID)
those in sets of 14 and then stripe those 4 into one big array.  We

want

to get the most spindles possible servicing disk requests and I wanted
to know if anyone has tried such a setup.

How big are your drives?  There's apparently a 2 TiB limit on raid
sizes,
there's even someone who has been asking if 12 x 160 or 13 x 160 is
ok(sorry, I don't have an answer for said person)

Mike

On Fri, 21 Feb 2003, Rechenberg, Andrew wrote:

Isn't it 2TB per RAID device (i.e. Linux block device) or 2TB in total?


I have 28 36GB 15K drives and 28 18GB 15K drives.

Sorry, I got the impression you were making one device of 56/2 = 28
drives in raid0
It should be per raid device, yes.

On Fri, Feb 21, 2003 at 11:03:27AM -0500, Rechenberg, Andrew wrote:

Isn't it 2TB per RAID device (i.e. Linux block device) or 2TB in total?

Linux has a 2TB block device limit.  There's a patch floating around to
increase that, but I don't know very much more than that.  Someone
around, or google, should know more.

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