Subject: Re: type-length-value chains for FFS (was large Inodes)
To: Neil A. Carson <>
From: Bill Studenmund <>
List: tech-kern
Date: 03/24/1999 18:01:03
On Wed, 24 Mar 1999, Neil A. Carson wrote:

> > Doh! I mis-read mc's output. :-( You're right that that size is achievable
> > now. ;-)
> Isn't it in fact one terabyte, because a daddr_t is signed? (to allow
> referencing of the indirect blocks by a vnode via negative numbers)

Actually it's not a problem in ffs. ffs uses ufs_daddr_t's which are, as I
understand it, addresses of FFS blocks. i.e. on an 8k/1k system, they are
addresses of the 8k chunks. Thus with signed ufs_daddr_t you can have
2^31*8k worth of fs, or ~16 TB. Not enough? grow the disk blocks. 16k
blocks will give 32 TB, 32k -> 64 TB, and 64k -> 128 TB.

A bigger, more immediate, problem is that daddr_t is an int32_t. :-)

Take care,