Despite 64 GB of memory, why is my Mac slow?

Question

Level 1

133 points

Despite 64 GB of memory, why is my Mac slow?

Hello friends. Most of my work on my 2017 27" iMac is video editing in FCPX. In order to hasten up my workflow, I have purchased LaCie 1TB Rugged SSD PRO Thunderbolt 3 External SSD to use it as a scratch disk for my video editing. This SSD is connected by the Thunderbolt 3 wire to the Thunderbolt 3 port. Simultaneously, I have upgraded my memory from an earlier 16 GB to 64 GB [4x16 GB memory cards from OWC]. Despite this costly upgrade, I feel very sad that the transfer speeds are dismally slow. I have taken a screenshot of the transfer speeds when I was exporting a 50 minute project to my internal HD. Can anyone tell me what is wrong?

The read and write speeds were mostly below 200 MB/s! Have read that they should be reaching 2700 MB/s!

Regards

Posted on Nov 17, 2020 6:28 PM

Reply

Answer 1

padams35

Level 4

3,613 points

Nov 27, 2020 10:00 AM in response to somanna

I'm sorry this is only half as fast as expected, but 4-5x faster sustained write speed still sounds like a significant improvement to me.

For a simple transfer I would have expected just a drag/drop without using any Final Cut Pro resources. If there is more to what you are doing I'd suggest checking CPU use, GPU use, and then reposting in the Final Cut Pro forum section. https://discussions.apple.com/community/professional_applications/final-cut-pro

Reply

Answer 2

somanna Author

Level 1

133 points

Nov 26, 2020 11:03 PM in response to padams35

Hello and good afternoon from India!

This is to provide an update to my current problem. After equipping myself with the 500GB Sabrent SSD, I find that the transfer speeds have slightly improved: reads are above 2000 MB/s while the writes reach a peak of around 1300 MB/s but fall down to between 600 to 800 MB/s. When I peeped into Activity Monitor, I was disquieted to notice that there was no great usage of the 64 memory of RAM as indicated by this screenshot:

Only 8.71 GB of Memory and 8.05 GB were being deployed to transfer a 30 minute project from my 1TB LaCie Thunderbolt 3 SSD to my 500GB Sabrent Thunderbolt 3 SSD.

Might I know what the problem is? Why are the write speeds so slow? Why is there so little of the 64 GB of RAM being utilised? Is there any solution to obtain faster speeds of transfer?

Regards and take care.

Dr. Somanna

Reply

Answer 3

somanna Author

Level 1

133 points

Nov 27, 2020 6:16 PM in response to padams35

Thanks for this input. I just now transferred a 4.27 GB file from Sabrent to LaCie Thunderbolt 3 SSDs. The transfer took place in a jiffy...in the twinkling of an eye!

However, my desire to have faster export of FCPX projects remains unfulfilled. To address this problem, a very senior member has joined this thread and asked for the EtreCheck report. Let us see how he analyses and advises me in this matter.

Regards

Dr. Somanna

Reply

Answer 4

somanna Author

Level 1

133 points

Nov 27, 2020 6:19 PM in response to Old Toad

Good morning. Thanks for your willingness to help. I am sending you the report as additional text.

EtreCheck Report

Regards

Dr. Somanna

Reply

Answer 5

Nov 18, 2020 8:50 AM in response to somanna

Hi, welcome to the Apple Users Community.

Please confirm the RAM is correct for your unit.

Have you checked to see if it operating correctly?

How old is the cable and SSD?

What is the format of the SSD?

Best of luck

Reply

Answer 6

padams35

Level 4

3,613 points

Nov 18, 2020 9:08 AM in response to somanna

What's wrong is you are saving to the internal HDD/Fusion.

7200rpm HDDs usually top out at ~150 MB/s for sustained write operations, so that looks pretty normal to me. The only way to reliably get those 2000+ MB/s speeds is to move files between fast NVMe SSDs.

(If you your internal drive is an SSD then that's another problem).

Reply

Answer 7

somanna Author

Level 1

133 points

Nov 18, 2020 6:22 PM in response to Pete-Progressive-Graphics

Thanks for the welcome and thanks for your questions. The RAM cards have been purchased based upon the requirements for my iMac as can be understood from the screenshot below:

I don't know how to check whether the RAM cards are operating correctly, but this I have read: if any card is defective, the system will not turn on.

The SSD and cable are barely 2 months old. I have an additional new cable with me, a Belkin thunderbolt 3 cable. Perhaps I could use that cable ignoring LaCie's instructions not to use other cables.

The SSD is formatted to APFS.

Regards.

Reply

Answer 8

somanna Author

Level 1

133 points

Nov 18, 2020 6:36 PM in response to padams35

Thanks for this precious input. I have observed that when I export the project to an external USB 3 based SSD, the transfer speeds are around 450 mb/s. Presuming that I would get faster transfers when I have the internal HD [HDD/fusion], I had changed my destination to the internal HD but found out that the speeds had slowed down greatly. At the initial stages of the export, the speeds crossed 1500 MB/s, but shortly, they fell down to around 150 MB/s.

From your reply I have learnt what the problem is. I stay in India and procuring the Thunderbolt SSD and the OWC's RAM cards from the United States were a tough and costly affair.

I have no idea of what NVMe SSDs are? Are they external drives attached to the Mac by Thunderbolt 3 cables? I will do my study on this, but if you can provide some information, it will be helpful.

Regards

Dr. Somanna

Reply

Answer 9

somanna Author

Level 1

133 points

Nov 18, 2020 6:41 PM in response to padams35

Dear padams35, I found these on India's Amazon:

These seem like memory cards. Can you direct me regarding how these can be installed in my Mac? Will an Apple technician be able to do it?

Regards

Dr. Somanna

Reply

Answer 10

padams35

Level 4

3,613 points

Nov 19, 2020 5:34 AM in response to somanna

Overly simplified there are basically two types of SSDs: SATA (~500 MB/s) and NVMe SSDs (1500-3000 MB/s).

Apple technicians can do the upgrade, but will probably insist on using OEM Apple parts. Especially since iMacs use a custom non-standard connector. OWC sells 3rd party SSDs using that connector and has install videos, but if you have an unused Thunderbolt port I'd suggest taking the easy path and using an external drive.

For an external drive you have:

Cheap: USB 3.1 M.2 NVMe (or PCIe) enclosures. Limited by USB-C to a maximum of ~1200 MB/s.

Premium: Thunderbolt 3 M.2 NVMe (or PCIe) enclosures. Can run up to ~2600 MB/s, but usually limited by the SSD's speed.

Alternatively you can find prebuilt USB 3.1 or Thunderbolt 3 external SSD devices/bundles like your LaCie 1TB Rugged SSD PRO (also an NVMe SSD).

Reply

Answer 11

somanna Author

Level 1

133 points

Nov 19, 2020 6:18 AM in response to padams35

Thanks for your valuable advise. I too have been studying up on what is new territory for me, but your above post has greatly helped me to understand the problem.

My Mac is under warranty till Feb 2022 and having the Mac opened by non-Apple folks has to be ruled out.

I wish to know what you think of this external drive sold by Sabrent, which I think can be connected to my other Thunderbolt port:

https://www.amazon.in/Sabrent-Thunderbolt-External-2400MBs-SB-XTRM-500/dp/B07XR5KY3H/ref=sr_1_9_sspa?dchild=1&keywords=Thunderbolt+3+SSD+external%2C+250+GB&qid=1605794693&sr=8-9-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzRkNKS1o4RThKSk1ZJmVuY3J5cHRlZElkPUEwMDM4NDMwR0ZaSExIMUlZMFJUJmVuY3J5cHRlZEFkSWQ9QTA5NzQ5OTgzRFpSWlk2OFBTOE5OJndpZGdldE5hbWU9c3BfbXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==#customerReviews

Regards.

Reply

Answer 12

somanna Author

Level 1

133 points

Nov 19, 2020 7:38 AM in response to padams35

I have ordered one just now and will be getting it by Sunday...and then I hope to work at blazing speeds😀. Shall let you know as and when I am able to export a fresh project to this new SSD.

Take care.

Dr. Somanna

Reply

Answer 13

Old Toad

Level 10

215,268 points

Nov 27, 2020 12:21 PM in response to somanna

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to include the report in your reply.

IMPORTANT: ⬇︎ ⬇︎ ⬇︎

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem.

Reply

Answer 14

padams35

Level 4

3,613 points

Nov 19, 2020 6:37 AM in response to somanna

Seems to be a fine choice. You've found a fast Thunderbolt-3 SSD with good reviews. Also I've used Sabrent stuff before and been satisfied.

Reply

Despite 64 GB of memory, why is my Mac slow?

Similar questions