In Isilon OneFS, what is a characteristic of CoW with snapshots?

The correct answer is A. Used for small changes, inodes, and directories. With copy on write, as the name suggests, a new write to HEAD results in the old blocks being copied out to the snapshot version first. Although this incurs a double write penalty, it results in less fragmentation of the HEAD file, which is better for cache prefetch, etc…

Isilon Concepts and Architecture

Question

Options

AUsed for small changes, inodes, and directories.
BAvoids the double write penalty.
CIncreases file fragmentation.
DUsed for more substantial changes such as deletes.

How the community answered

(44 responses)

A
73% (32)
B
5% (2)
C
14% (6)
D
9% (4)

Explanation

With copy on write, as the name suggests, a new write to HEAD results in the old blocks being copied out to the snapshot version first. Although this incurs a double write penalty, it results in less fragmentation of the HEAD file, which is better for cache prefetch, etc. Typically, CoW is most prevalent in OneFS and is primarily used for small changes, inodes and gen-data-protection-snapshot-iq.pdf

Topics

#CoW#snapshots#inodes#data protection

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