RE: Flash disks and FFS layout heuristics



-----Original Message-----
From: Matthew Dillon [mailto:dillon@xxxxxxxxxxxxxxxxxxxx]
Sent: Monday, March 31, 2008 1:06 PM
To: Martin Fouts
Cc: qpadla@xxxxxxxxx; freebsd-arch@xxxxxxxxxxx; Christopher
Arnold; arch@xxxxxxxxxxx
Subject: RE: Flash disks and FFS layout heuristics


But how do you index that information? You can't simply
append the information to the NAND unless you also have a way to
access it. So does the filesystem have to scan the NAND (or
significant
portions of it) in order to build an index of the filesystem topology
in
system memory?

No matter what you do you have to index the information
*SOMEWHERE*.

And NAND devices have a *SOMEWHERE* that makes them different than other
persistent storage devices in ways that make them interesting to do file
systems for.

It's not _that_ you have to scan the NAND, by the way, it's _when_ you
scan the NAND that has the major impact on performance.
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