> > Would I also be right in thinking that if we were able to do one more
> > level of indirect block, we would multiply the capacities by B/4 in
> > each case, giving capacities of 4T, 64T, 1E and 16E for ext2 file
> > systems using 1k, 2k, 4k and 8k blocks respctively?
> Yes.
Hold it, If I remember correctly, block numbers are still 32bits. So
you're limited to filesystems of 4T, 8T, 16T and 32T anyway.
If we move to extents, we can start to do nifty stuff: there is a
32bit start block number, and a 32bit length field in an extent. That
length field is WAY over dimensioned. You can grab a few bits there for
"move to another meta-group". Meta-group being a group of 4G blocks.
We're two bits past the 4G mark on common disks now. We consume half a
bit per year. So we'll reach the 4T filesystemsize limit in about 16
years. (Specific users will hit the limit earlier).
So this all isn't too close yet, but whenever disk-formats are
redesigned, we should think about what we'll do about it. (I wouldn't
worry about the extra indirection level, I'd solve that with larger
blocks: that goes with the fourth power. So adding a bit to the
blocksize gives you 8 more years before it becomes a problem again,
and by that time, the cost of wasted memory etc etc isn't an issue
anymore).
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* ------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------
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