MacLife - USA (2020-09)

YOUR MAC

CACHES DATA

LIKE A SQUIRREL

STORES ITS

NUTS!

Software updates can be very

big. The direct download of

the macOS Catalina 10.15.4

update was 3GB, while the

same month’s iOS download was 4.17GB.

That’s a lot when you just have one device

to update, let alone multiple Macs or iOS

devices. Wouldn’t it be great if you could

download something once and then share

it with all the other devices that need it?

And wouldn’t it be great if you could do

the same for app updates, iCloud data, and

Apple Books? Say hello to content caching.

WHAT IS CONTENT CACHING?

Content caching speeds up software

updates and iCloud downloads by keeping

a local copy of data you would normally

have to download from Apple. The term

caching comes from the French word

cacher, which means “to hide.” When

a squirrel creates a store of nuts to last

through the winter months, that’s

a cache. On your Mac, the nuts are the

data you want to share.

Caching is well established in the

computing world.

Cache memory is used

by processors and

graphics processors

to get quick access to

commonly used data.

Data from hard disks or

SSDs is cached for faster

access. And in the case

of content caching,

which is what we’re

interested in here, data

from Apple’s servers is

stored locally and shared

on the network with

your devices. Instead

of having to download

the same things again

and again, cached data is

downloaded once then

shared locally.

Content caching

Speedier updating for all your devices

HOW DOES CONTENT CACHING WORK?

With content caching, you have a Mac

that takes care of the cache. All your other

devices become its clients, and when they

ask for something their request goes to

the Mac. It looks at the request and asks,

“Do I have this already?” If the answer is

no, the client device downloads it from

Apple and the Mac takes a copy of it for

the cache.

The next time a client device asks for

that content, the Mac already has it — so

instead of having to connect to Apple’s

servers again, the client device is given

the data it needs directly from the cache.

WHAT IF MY NETWORK ISN’T A SIMPLE

SUBNET? WHAT IF IT’S MORE COMPLEX?

By default, content caching expects you to

have a pretty simple network: everything

connects to the same router or NAT

storage device on the local network. But

you can also use it on more complex

networks and run multiple content

caches, which become peers of each

other. If one cache doesn’t have what

a client wants, it checks with the other

cache(s) before going online. Apple

provides details at bit.ly/mac354chng.

WHAT KIND OF CONTENT GETS CACHED?

Content caching works slightly diļerently

on Macs and on iOS/iPadOS devices. On

your Mac, it can cache macOS updates and

Internet Recovery images (but not for

macOS older than 10.13.5); apps and their

updates from the Mac App Store;

downloadable content for GarageBand;

iCloud photos and documents; Apple

Books; and Xcode downloadable

components for Xcode 10.2 or later.

On iOS and Apple TV, the supported

content includes over–the–air updates for

iOS and Apple TV; Apple TV screensavers

for tvOS 12.2 up; iOS and Apple TV apps

and updates; on–demand resources for

iOS 10/tvOS 10 and later; iCloud data for

YOU WILL LEARN

What content caching is

and how to use it across

your devices

HOW IT

WORKS

Image rights: Apple.

17.221.45.7

Local network

Router/NAT

Internet

10.00.2

Local content cache

10.00.3 — 10.0.0.12

Clients

Create

84 SEP 2020 maclife.com