Service: Apple Caching Server

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October 29 2014: 

We have put into place a second caching server to peer with our existing server.  Over the last year we found that, while not completely stable, the caching server has been a huge benefit when it comes to the larger scale downloads for Apple (Mavericks, Yosemite, iOS 8.1, etc).

In just the past few weeks we have served 240GB of apps, patches, and updates from the server while only downloading 74GB directly from Apple.  

Since the Fall 2014 semester started the CalArts internet connection has seen record usage, so any elimination of unnecessary downloads is a direct benefit to our community as a whole.

November 23 2013:  

The caching server has now been in place for over three weeks and I have some initial numbers to report.  So far we have cached just over 72GB of apps, updates, and iBooks: 29.2GB for OS X, 40.59GB for iOS, 16.3MB for iBooks, and 2.19GB of other (I have not determined what this consists of just yet).  We have distributed 280GB of these apps and updates from the caching server.

Our observed download speeds (from Apple servers) are usually around 4MB/s.  These same downloads from the caching server average 12MB/s, peaking at over 40MB/s.  The difference in speed is due primarily to the size of the download; most apps and updates are too small to reach peak speeds.

Now, to the actual benefit of the caching server:

At 4MB/s downloading the 280GB worth of data (that the caching server has distributed) would take 19.4 hours.  If we consider just the average speeds (4MB/s to 12MB/s) we can extrapolate that downloading the same content has taken around 6.5 hours, saving CalArts Faculty, Staff, and Students 12.9 hours of staring at progress bars.

Now, 12.9 hours doesn't sound like much, and frankly it isn't (~2% total time in a three week period), but the real benefit to the caching server will be coming when a major update, like OS X 10.9.1 or iOS 7.1, is released.  These saturate the CalArts internet connection, are generally quite large, and could easily hit the 40MB/s peak speeds we have seen so far.  

I'm very much looking forward to dissecting those numbers!

November 7th 2013:

I am very happy to announce that we have put our new Apple Caching Server into operation!  The caching server will help eliminate the need to download OS X updates (OS X 10.8.5+), iOS updates (iOS 7+), iBooks, and applications from either iOS and OS X App Stores.  Instead these downloads will come from the on-campus caching server.


Whenever someone downloads an update, iBook, or App from Apple a copy is simultaneously downloaded to the caching server.  The next time that update, iBook, or App is downloaded on campus it will be sent from the caching server at a much faster rate than downloading it from Apple.  

We are specifically excited to see how this improves our service when the next version or update to iOS or OS X is released.  When these updates are released it puts a huge strain on our internet connection, slowing everybody down and sometimes interrupting classes that rely on services like YouTube.

With the caching server in place we will be leveraging our local network speed to allow wired and wireless clients to rapidly download commonly used Apple Apps, updates, and iBooks.  There is absolutely nothing to do in order to use the caching server -- if you're on campus your Apple device running 10.8.5+ and/or iOS 7 will be automatically directed to it!

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