What's slowing down my Mac? I have the following mac:


iMac (27-inch, Late 2013)
3.4 GHz Intel Core i5
8 GB 1600 MHz DDR3
NVIDIA GeForce GTX 775M 2048 MB


It has a HDD, and I have 240GB out of 1TB free space.

I'm on OS X El Capitan (10.11.3).

Since some time this mac has been very, very frustratingly slow. It takes about 15 minutes to go from a clean boot to getting firefox up and running. Especially starting applications is painful. It's a bit hard to quantify though, because at other times it seems ok. There's a big perception/psychology part to it.

I'm considering doing a fresh install, and perhaps go with an older OS X. But I'm also just extremely curious what's causing this. I can't figure it out. I know HDD's are slower, but the machine was fine when I got it, and I find it hard to believe that newer OS X's are so much worse.

Here's a few things I've done:


Turn off time machine, for good measure.
Turn off dropbox. My dropbox is rather large and I noticed it can be a pretty big factor when it's indexing.
I don't use FileFault.
1Password is in the startup items, nothing more.
I recently did a scan of my disk in recovery mode, to ensure that the disk wasn't failing. S.M.A.R.T. says verified.


There's nothing out of the ordinary in Activity Manager / htop. CPU and Memory both seem reasonable. Also worth mentioning that if I start a game like Starcraft or Cities Skylines, these applications perform pretty well once started. Starting them takes a long time though.

I'm basically at a loss why my fairly new Mac is worse at running applications as back when I got my first white macbook in 2006, when the applications I'm running haven't changed (firefox, terminal, thunderbird), and Memory quadrupled.

I'm very comfortable with the command line, and I just want to satisfy my curiosity. What causes my computer to take 15 minutes to go from boot to Firefox? How can I measure what the computer spends time on? Are there maybe obvious performance improvements I missed?

diskutil list output:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            999.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3


A few (maybe) interesting items from system.log:

I got a bunch of these:

Mar 20 19:13:18 localhost kernel[0]: Sandbox: launchd(1) System Policy: deny(1) file-write-flags /private/var/run/dyld_shared_cache_x86_64h
Mar 20 19:13:18 localhost kernel[0]: Sandbox: launchd(1) System Policy: deny(1) file-write-unlink /private/var/run/dyld_shared_cache_x86_64h


A whole bunch of these for all my applications:

Mar 20 19:15:44 Pasta kernel[0]: Sandbox: coreduetd(74) deny(1) file-read-metadata /
Mar 20 19:15:44 --- last message repeated 23 times ---
Mar 20 19:15:44 Pasta kernel[0]: Sandbox: coreduetd(74) deny(1) file-read-metadata /Applications/App Store.app
Mar 20 19:15:44 --- last message repeated 4 times ---
Mar 20 19:15:44 Pasta kernel[0]: Sandbox: coreduetd(74) deny(1) file-read-metadata /Applications/Automator.app
Mar 20 19:15:44 --- last message repeated 4 times ---
Mar 20 19:15:44 Pasta kernel[0]: Sandbox: coreduetd(74) deny(1) file-read-metadata /Applications/Calculator.app
Mar 20 19:15:45 --- last message repeated 4 times ---
Mar 20 19:15:44 Pasta kernel[0]: Sandbox: coreduetd(74) deny(1) file-read-metadata /Applications/Calendar.app
Your machine should not be this slow.  If the below doesn't help, you can take it to an Apple store to run hardware tests.  I've seen instances where faulty sensors, for example, would cause the computer to go into limp mode, and the hard drive was fine.

Have you tried resetting the PRAM?

There are some command line utilities that should be able to pinpoint what's using the disk (if that's the case).  You can try iostat 1 - this will display general disk activity, refreshing every second.  

To see more granular info such as the process, use "fs_fsusage": sudo fs_usage -f diskio

I'd first try to narrow down what's eating all the I/O using the above commands.  You can always wipe and reinstall if you want, but if you restore your entire Time Machine backup, you'll be potentially re-introducing the problem.  So I'd say only restore your data/ user account w/o the ~/Library folder if possible.

On the hardware side of things, these devices shipped with at least 7200 RPM drives.  While much better than the slower 5400, modern OSes will still choke with excessive disk activity (spotlight, time machine, various system services).  

Replacing the drive with an SSD on your own IS possible but you need tools, and have to be very careful handling the screen.  So if you've never done it before I'd recommend paying someone to do.

EDIT: Also check your system log in Console... look for disk i/o errors