03-06-2018 02:32 AM
I have upgraded my old hard drive on my iMac 2013 to a Crucial MX500 (500 GB SSD).
I did a clean install of High Sierra, (after formatting the SSD to APFS using Disk Utility).
I have enabled TRIM in Terminal.
The iMac is now painfully slow - read/write speeds to the SSD are around 150-200, all processes slow.
Any pointers appreciated.
iMac 27 Inch, late 2013
16GB 1600 MHz DDR3
NVIDIA GeForce GTX 775M 2 GB
03-06-2018 08:39 AM
I'm using Blackmagic Disk Speed Test, a cycle of around 5 minutes,
Yes, I am booting from the SSD.
The problem is beyond the read/write speeds, every process is sluggish.
03-06-2018 02:49 PM
Be careful running extended write tests as I had it adversely affect performance on an MX300 SSD and the only way I could regain performance was by performing a Secure Erase on the SSD. Short write tests are fine. The MX300 & MX500 series along with other TLC NAND SSDs have poor extended write perfomance due to the nature of TLC NAND.
Make sure your computer is not Filevaulting (I know Apple is starting or is going to start Filevaulting laptops by default). Go to System Preferences, Security & Privacy, then click the FileVault tab to check the status.
Open Activity Monitor located in the Utilities folder and select the Disks tab and check on the disk activity in the lower right (Data read/sec & Data written/sec). If this number is constantly in the MB range, then try to determine what is reading or writing to the SSD. (Spotlight, macOS updates, Anti-Virus scan, Filevaulting etc.)
You could also check the Console system logs to see if anything is showing up there. They are hard to read, but if you see a lot of stuff being repeated or a lot of similar errors, it might be affecting performance.
A quick search online reveals several recent forum posts about High Sierra and a slowness issue and the use of Trim on third party SSDs. While Apple made it easier to enable trim on non-Apple SSDs, I'm not sure it is guaranteed to work without issue. If you disable Trim, does the iMac perform properly? If so, I would just leave it disabled. I've read multiple articles on the pros & cons of Trim in general and some of the articles against using Trim are pretty convincing that it is not needed and could impact performance in certain situations. (I don't have links to them as I read them a long time ago.) I know some Linux distributions such as Debian blacklist certain SSDs from using Trim as it has been found to cause data loss I believe.
03-07-2018 02:45 AM
Update: I've performed a clean reinstall of Sierra after formatting the SSD HFS+ and the OS is more stable.
However, I am still experiencing extremely slow read/write speeds (200Mbs).
This is with TRIM enabled/disabled.
Is it worth mentioning that when the new drive was installed the original cables were used to connect the SSD?
03-07-2018 05:41 AM
However, I am still experiencing extremely slow read/write speeds (200Mbs).
Does your computer support sata 3? if not, it's maximum drive speed is ~260MB/sec. Unless it uses an nvidia motherboard in which case it'll be even less than that.
03-07-2018 01:20 PM
I would suggest connecting the SSD using an external USB 3 SATA Adapter to see what numbers you get as that would eliminate the internal controller and cables. Testing it as an external boot device and testing it externally while booted from your original internal drive could prove interesting.
Also, you could try performing a Secure Erase on it, then (assuming you have access to a USB SATA adapter) just format it with HFS+ and run the tests again. A Secure Erase requires the SSD to be installed to an internal controller.
It might be interesting to see the SSDs SMART Attributes before a Secure Erase. You can use the free app DriveDX to show a screenshot of the SMART attribute table. Note that checking SMART Attributes when booted using OSX requires the drive being inspected to be installed internally. (I've found DriveDX to report false failures for SSDs due to its method of interpreting these attributes, but it is Ok to use for viewing the attributes.)
03-14-2018 01:42 PM
I've run the SMART Attributes test using DriveDX, all appears to be OK.
Looking at the Activity Monitor - the kernel task CPU reading is permanently off the scale.
I did install Mac Fan Control as the fan was spinning too fast after the SSD upgrade.
Using an external USB adapter is not an option I'm afraid, I've already had to replace the screen as the original one broke whilst removing.
03-14-2018 06:27 PM
Power on your iMac and immediately hold down the Option key so you get the Boot Picker menu. Stay on this menu for a few minutes. Does the fan run at high speed? If so, you likely need a Thermal Sensor Harness to use with the SSD so the iMac knows what the drive temperature is. When a temperature sensor is missing or non-functional, Apple's computers default to the fans running at high speed as a safety precaution to make sure the system is not overheating. Recently Apple has been modifying their drive's firmware and using the drive's internal temperature sensor instead of using an external sensor.
See the comments by Robert & Dan at the end of the iFixIt Hard Drive replacement guide for this iMac.
If the fan runs at normal speed at the Boot Picker menu, then try a Safe Boot. Hit enter at the Boot Picker screen to boot to your SSD and immediately hold down the Shift key so you perform a Safe Boot which will disable most non-essential drivers/extensions. Do you still have the performance issue and high CPU utilization? Your display may flicker and act oddly since Apple doesn't load a full video driver when doing a Safe Boot. If performance & CPU utilization are good in Safe Boot, then you should investigate the driver/extensions that aren't loaded in Safe Boot.
Boot the iMac normally and in the Apple System Profiler (click on the Apple menu and hold down the Option key and select System Profiler) check on the SATA information and see what the negotiated link speed is for your SSD. There is another post on these forums where a 2009 Mac Mini won't allow the SSD to run at full speed due to a known compatibility issue with the NVidia chipset and your iMac is using an NVidia chipset.
FYI, I've never noticed any CPU utilization issues with missing thermal sensors, but I've also never tried it with Sierra or High Sierra.
Does the performance issue occur after a clean install and before installing 3rd party applications? Does the CPU utilization issue occur before 3rd party software is installed? Make sure no external devices are attached except for the keyboard & mouse.
If it is not the temperature sensor issue and no 3rd party software or any external devices are attached and you still have this problem, then you probably should contact Crucial Support directly to report the issue.
07-18-2018 10:30 AM
Apolgies for the delay in responding.
I've followed your suggestions with the following results:
"Boot Picker menu. Does the fan run at high speed?" - Yes
"Safe Boot. Do you still have the performance issue and high CPU utilization?" - Yes
"SATA information and see what the negotiated link speed is for your SSD." - 6 Gigabit
"Does the performance issue occur after a clean install and before installing 3rd party applications?" - Yes
"Does the CPU utilization issue occur before 3rd party software is installed? " - Yes
I created an external boot drive (USB3) as an alternative to compare the performance and if anything it was even worse.
The Mac Fan Control software works perfectly well in controlling the fan speed - does the thermal sensor do anything that the software doesn't?