Exercise 2: Why Extents Beat Block-by-Block Mapping for a Large Video File — Possible Solution
====================================================================

Explanation:

Per the chapter's own description, block-by-block mapping (ext2/ext3's
own approach) tracks a file's data location as "a long list of
individual block pointers" -- for a large, mostly-contiguous video
file spanning potentially hundreds of thousands of individual disk
blocks, this means the filesystem has to store and manage a
correspondingly enormous list of individual pointers, one per block,
even though most of those blocks sit physically right next to each
other on disk in one continuous run. This is a real, direct source of
metadata bloat -- the amount of bookkeeping data needed grows
proportionally with the number of individual blocks, regardless of
how contiguous they actually are.

Extents solve this specifically for the common case of large,
contiguous files. Per the chapter's own description, an extent
represents "a large contiguous run of blocks as one compact record --
'blocks N through N+1000 belong to this file'" -- rather than one
pointer per block, a single extent record can describe an entire
contiguous stretch of the video file with one small entry. For a video
file that's mostly written in one contiguous pass (as most video files
genuinely are), this means the ENTIRE file, or nearly all of it, can
be described by a small handful of extent records instead of
potentially hundreds of thousands of individual block pointers --
dramatically less metadata to store and manage, and, per the chapter's
own point, reduced fragmentation-related overhead as a direct
consequence of needing to track far fewer individual entries.

WHY THIS WORKS AS AN ANSWER
------------------------------
This contrasts what each approach actually stores (one pointer per
block vs. one record per contiguous run) and explains why a large,
contiguous file specifically benefits from the extent approach's own
compact representation, rather than a generic "extents are more
efficient" claim.