That may sound hyperbolic, but in terms of general performance and lag, it is easily the worst OS I have ever used, it's consistently awful on my 3 mac os computers: retina macbook pro, hackintosh desktop, and a 2012 12-core Mac Pro.
How does Apple get away with this? Are the software engineers at Apple this incompetent? It's a hilariously awful OS, and the slowest I have ever used.
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I don't think you are exaggerating about the problems you are experiencing with Yosemite.
I made the fatal mistake of upgrading to Yosemite on both my 2011 MacBookPro (8GB RAM. 500GB HD which was only half full) and 2011 iMac 12,2 (16GB RAM, 1TB HD which has over 300GB free) - ie on machines with plenty of RAM and HD space.
MacBookPro Disaster - and lessons learned
To my horror, the MBP became severely crippled. The cursor lagged and keyboard response was so slow, it was virtually unusable, due to the extremely slow response time. Logging into the App store took ages. I downloaded system Apps to see what was going on with the system, and discovered that even with the cache cleared, and just the finder, and App store open, the machine was using 99% of RAM.
I assumed the Download was corrupted, and tried to Download it again, discovering a new problem - the MBP was frequently dropping off the Wifi. I checked, and so was the iMac. I contacted our ISP who said their connection was fine. So I did a speed test using a Chromebook on the same network. Our DL speed was 20Mbps, upload 9Mbps (ie fine) - but an app I used that tested the connection speed showed the Mac (when it was connecting to the Wifi at all) was transferring data to the router at less than 30kbps.
Turns out that this is a common problem
https://discussions.apple.com/thread/6995894?tstart=0
I then tried to re-install the system. BUT - I had encrypted the hard drive, and it turns out that Apple changed how Core Storage works (back at Lion OS) - and I could not re-install the system, or downgrade using a flash drive to any older system. Turns out, this fatal Cold Storage error is a common problem.
https://discussions.apple.com/thread/6603651?start=0&tstart=0
I tried various suggested solutions found online - but no joy.
Finally I took it to a specialty Mac repair centre. They said the machine (bar the hard drive) was OK - but the hard drive (which otherwise tested OK) was non-functional because it was not possible to install the system on it
iMac Saga - read this if you worry about cost of data and value your privacy
It would be fair to suspect that it might have been because the MBP was an old machine that the above occurred, but like you I had upgraded both Macs at the same time. This was because I'd (with reluctance) upgraded the iOS on portable devices, and had been prompted to upgrade the Mac OS. It turns out that Yosemite has (IMO a highly problematic) persistent Notification issue - that you can't disable. (Check upper right corner of your screen). This includes notifications of upgrades from the App store, which you can't disable. At best you can get the notice off the screen, by clicking a remind me (at the latest) tomorrow button.
The other issue is Yosemite may be syncing - despite turning syncing options off. (Other people complain of this. Others have problems with lack of Syncing).
Here are good suggestions for iOS, OS iCloud Syncing issues
http://osxdaily.com/2015/03/16/fix-itunes-12-ios-8-sync-issues/
I don't want to automatically sync data or pics to the cloud, app stores, other devices or anywhere. Nor do I want to be forced to do it.
If I did want to sync, I'd want to be able to specifically select what data, and specifically select from which device and to which device or cloud service. I got turned off syncing years ago when my Mac synced my computer email address book (which did not have phone numbers) to my phone - and wiped out phone number data. IMO, syncing in it's minimally uncontrollable state - sucks.
Any App that repeatedly checks for updates, or repeatedly syncs - will consume bandwidth. Bandwidth is expensive. It ought to be possible to disable Notifications (or anything else that unnecessarily consumes bandwidth like syncing), individually or as a group. It certainly ought to be easy, and obvious how to control syncing on an individual App basis.
Back to the iMac. The iMac displays the same symptoms as the MacBook Pro, but is fortunately, for some unknown reason, not as bad. Its computer to router speed is between 30kbps - 2.2 MBps down, to 20kbps-1.2 Mbps up - far lower than the ISP speed of 20Mbps down, 9Mbps up. It also frequently drops the connection to the router.
With just the App store and finder on - the iMac also consumes 99% of 16GB of RAM!!!!
If I disconnect from the App store and Internet and clear the RAM, RAM usage drops to ~20%.
There is a lag with typing, especially on start-up. And for some reason Apps (even ordinary ones like Preview) repeatedly hang. The hanging of Apps improves after RAM is freed after using a cache clearing App. But this has to be done multiple times a day!
As my MBP was out of commission and iMac running slow with obscene RAM usage I checked for an App to get a better idea of what was likely going on with the Network
If you want to know what's going on with your Network (and are prepared to be horrified) I would strongly recommend the App Store App -
Graphical Network Monitor.
It shows the Application, local IP address, remote IP address, status of the connection, amount of data moving up and down and location of the remote server. (You can check out who owns the remote servers shown by checking the IP address on:
https://who.is/
I don't know what's going on, or what the implications are for RAM usage or poor performance of Yosemite or privacy (or if this is normal, and not necessarily related at all) - but
even with no syncing on and only the App store turned on, there seems to be a massive amount of data uploaded from my machine - even when not actually browsing the Internet or downloading anything from the App store - just with them on.
I got AdBlockerPlus extension and EFF's Privacy Badger. PPP is off. But there was no improvement in this IMO alarming behaviour.
Graphical Network Monitor shows multiple instances of what looks like same Apple and chrome apps - with different connections, uploading and downloading. Activity dramatically increases even if you just click on Categories in the App store
Tested it on an online retail site and it went bonkers - necessitating scrolling through all connections and uploads/downloads - even though did not click on any item.
Does anyone know if this is normal or is it mega corporate spying? Is this likely affecting RAM or computer performance? Does this indicate a data security issue on the Mac?
I am not a computer geek, but am a very experienced Mac user. I have used Apples from the Apple II (in the 1970s) on - ie for eons - but am now considering changing platforms as this is such bad performance. Having to get a new hard drive or even a new laptop because of Apple Core storage issues is not on.
It does not appear to be affecting everyone (which may be why Apple seems to be ignoring this); but whatever is consuming RAM on Macs, interfering with wifi connections and severely affecting Mac performance is not benign - and Apple needs to sort it.
The culprit seems to be the Yosemite operating system.
What do you think?