Why does it take so long to upgrade to High Sierra?

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Level 7

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Why does it take so long to upgrade to High Sierra?

I just finished upgrading 4 of my Macs to High Sierra and am wondering why it takes so darn long to upgrade. Among the 4 Macs the upgrades each took from 1.5 to 3.0 hours.

Not a complaint, but what the heck is the system doing all that time? It has to be doing way more than just expanding compressed files and writing them to disk. The 5.2GB installer only took about 7 minutes to download and I assume that included the full new OS. In all cases the installations were to a primary, 250GB partition dedicated to macOS & applications (no data). The installed macOS (High Sierra) seems to be only about 15.2GB.

System details & upgrade times

macMini - 2.6GHz i5, 8GB RAM - nearly 3 hours (Yosemite to High Sierra)

Yosemite 10.10.5 to High Sierra 10.13.2 + supplemental update

MacBook Pro - 2.3 GHz i7, 8GB RAM - about 2:00 hours (Sierra to High Sierra)

Sierra 10.12.6 to High Sierra 10.13.2 + supplemental update

After the first two Macs, I timed the next 2:

27" iMac - 2.7GHz i5, 12 GB RAM - 1:35 hours (Sierra to High Sierra portion of the full upgrade)

Lion 10.7.5 to Sierra 10.12.6 (had to do this first; took about 2 hours)

Sierra 10.12.6 to High Sierra 10.13.2 (1:10 for High Sierra, additional 0:25 for the supplemental update)

21.5" iMac - 2.5GHz i5, 4GB RAM - 2:00 hours (Sierra to High Sierra)

Sierra 10.12.6 to High Sierra 10.13.2 (1:30 for High Sierra, additional 0:30 for the supplemental update)

Even more puzzling is that in the case of the macMini and the 21.5" iMac, at what I now know was the end of the upgrade process, the Macs just sat there with a black screen. At the time I was concerned something had gone wrong at the very end. After letting 15-20 minutes go by with no response from the Macs, I took a chance by tapping the keyboard space bar and the screen came right up as if the Mac had been in some kind of sleep mode all along. (The upgrade times I quoted don't include the apparent sleep time at the end.)

All the Macs are working fine on High Sierra. I'm just wondering what's going on all that time & why it takes so long.

iMac, macOS High Sierra (10.13.2), 27in/2.7GHz i5/8GB RAM/1TB+10TB

Posted on Jan 19, 2018 2:32 PM

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Answer 1

Jan 19, 2018 3:13 PM in response to MartinR

My guess is the main reason is because they all have HDDs. On SSDs or Fusion drives my experience has been 30-40 mins. How full the drives are, how much RAM, bus speeds and a host of other factors are involved.

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Answer 2

Kappy

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362,269 points

Jan 19, 2018 7:54 PM in response to MartinR

The installer contains a lot of compressed files that must be extracted and written to the disk. Then the compressed data are decompressed. The installer will have to locate each individual file in the old system and replace it with the new one from the decompressed new archive. This is under the overall control of a script. As you know a script is slower than a compiled application. Overall the upgrades are over 4-5GBs while updates are much smaller. There is also a lot of redundant error-checking during the installation. The data are a combination of binary and non-binary files. Suffice to say the overall process for an upgrade is pretty slow. And, this isn't taking into account any firmware upgrade that may be included.

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Answer 3

Kappy

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362,269 points

Jan 19, 2018 2:40 PM in response to MartinR

You are updating HDDs, correct? All upgrades (not updates) from earlier major versions. All computers have relatively slow CPUs. Assuming each computer's old system was in need of fixing prior to the upgrade forces the installer to take more time. I'd guess all of these cause the upgrades to take more time.

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Answer 4

Kappy

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362,269 points

Jan 19, 2018 3:15 PM in response to MartinR

Well, I suppose we could compare them to my 2011 3.4GHz or 2015 4.0GHz iMacs running i7 CPUs and have SATA III SSDs. Typical times for my 2015 iMac using an external SSD connected by Thunderbolt:

Install on a freshly erased drive: 25-28 minutes.
Reinstall of the same version of macOS: 45 minutes.
Upgrade an existing system: 35-40 minutes.
Complete a one-point update: 15 minutes.

Now, I've used 7200 RPM drives in all the laptops that I have. The oldest is from 2009 and the last one from 2011. All have i7 CPUs. I do have a 2015 MacBook but it isn't truly comparable. The laptops all take much longer than my iMac, but I haven't done any upgrades in a long time, but as best I can remember they took at least 2 hours to upgrade. I am simply not certain. It's an unreliable guess on my part. I simply remember I used to be able to prepare a meal and watch TV before they finished.

SATA laptop HDDs, even 7200 RPM disks, can be annoyingly slow compared to their bigger cousins which are not as slow but slow, nevertheless.

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Answer 5

John Galt

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Jan 19, 2018 3:17 PM in response to MartinR

There are many factors involved. The storage devices used (hard disk or SSD), the upgrade path from differing OS versions and the aggregate number of files requiring conversion to APFS (if applicable) are among them.

There is nothing particularly remarkable about the times you recorded.

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Answer 6

MartinR Author

Level 7

25,616 points

Jan 19, 2018 2:57 PM in response to Kappy

All these Macs have 7200rpm SATA-III HDDs and the upgrades were from a previous major version of macOS to High Sierra. Not sure what you mean about "all computers have relatively slow CPUs" - the CPUs in my Macs are running in the same speed range and similar architecture as the current lineup of iMacs and macMinis, and I don't think they are considered slow. At least, I don't consider them to be slow (I'd consider a 2006-era 1.8GHz CoreDuo slow by today's standards vs. my 2.7GHz quad-core i5.)

While I do think some of the upgrade time differences between the 4 Macs can be explained by differences in CPU, speed & RAM, I don't think those differences explain the consistently long time it took to upgrade each.

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Answer 7

Jan 19, 2018 2:35 PM in response to MartinR

I doubt if anyone here can give more than a generalization (none of us are Apple software developers).

Short non-scientific answer....it is a function of the code and what needs to be updated.

Barry

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Answer 8

Kappy

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362,269 points

Jan 19, 2018 3:52 PM in response to John Galt

What's the point of this, John? It's all been said already.

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Answer 9

MartinR Author

Level 7

25,616 points

Jan 19, 2018 7:39 PM in response to Kappy

OK, faster/fancier CPUs and drives make the installs & upgrades go faster. I get that.

But my question was ... what's the installer doing all that time?

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Answer 10

Jan 19, 2018 7:42 PM in response to MartinR

MartinR wrote:
But my question was ... what's the installer doing all that time?

Many things. If you want a minute by minute run down you are unlikely to get one.

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