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Re: 2 Terabyte File System Size Limitation

To: "Andi Kleen" <ak@xxxxxxx>
Subject: Re: 2 Terabyte File System Size Limitation
From: Steve Lord <lord@xxxxxxx>
Date: Tue, 05 Sep 2000 12:04:08 -0500
Cc: "Davida, Joe" <Joe_Davida@xxxxxxxxxx>, "'linux-xfs@xxxxxxxxxxx'" <linux-xfs@xxxxxxxxxxx>
In-reply-to: Message from "Andi Kleen" <ak@xxxxxxx> of "Tue, 05 Sep 2000 17:26:14 +0200." <20000905172614.A21975@xxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
> On Tue, Sep 05, 2000 at 09:18:04AM -0600, Davida, Joe wrote:
> > Is what Bill Jones is saying correct?
> > I am just starting on XFS, and dont
> > have enough familiarity with it's
> > architecture.
> 
> The LVM trick he proposes will not work on current Linux
> or Linux/XFS (at least not without changes to LVM). So you
> have a 2TB limit. 1TB may be safer due to possible 
> driver signedness bugs. 
> 
> 
> -Andi

I think the safest comment to make at the moment is that the path of least
resistence to getting above the 2 Tbyte limit is probably a kiobuf enabled
version of LVM, this path too has 2 Tbyte limits in it at the moment. 

ll_rw_block and generic_make_request are the places where the across the
volume limit is getting imposed. If we could make it to a remapping request
function without having to map a disk address through a 32 bit sector number
then it should be doable.

The other end of the pipe is the XFS inode number, and I am still not
convinced that mkfs options can tune the filesystem to get above the
2 Tbyte boundary, a mount option which restricts inode placement to
within the first 2 Tbytes of allocation groups should not be too hard.

Steve



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