Internal Drive Performance Check - EtreCheck report question

The SSD in the 21.5" iMac is an NVMe SSD which is much faster than the SATA based SSD found in the 27" iMac, but it is hobbled by the slow hard drive in the Fusion Drive setup. I'm also not certain which of the two SSDs you are booting from on the 27" iMac. If the OWC SSD is a fairly recent purchase from the last several years, then you may need to enable TRIM on it using the following Terminal command:

sudo  trimforce  enable

You will be prompted for your admin password, but nothing will appear on the screen as you type. Press the "Return" key to submit the password. You may need to run Disk Utility First Aid on the OWC SSD's volume in order to force an immediate TRIM event to occur (I'm not certain if this can be done while booted into macOS or if it may require booting into Recovery Mode using Command + R).

As the others have mentioned, seeing a complete copy of both EtreCheck reports is just as important as other factors may be involved as well. It is best to give EtreCheck "Full Disk Access" so the report contains more details which may provide more clues. Post the reports here using the "Additional Text" icon which looks like a piece of paper.

jhrichmond wrote:

If I do the steps to enable TRIM, will I lose data - does it reset the drive / wipe it?

No, it won't affect your data already on the drive. TRIM only erases the blocks awaiting to be re-used.

What does TRIM do anyway, and if. it is important, why is it not set to on automatically?

I'm not entirely sure, but Apple may just be playing things safe since they cannot guarantee all third party SSDs support the TRIM command feature.

Whenever you write data to an SSD, the data on the existing NAND memory block of the SSD is transferred to another block along with the new data to be written. The data is now contained on the new NAND block. The original NAND block now must be cleared (aka wiped or zeroed) before that NAND block can be re-used. These used NAND blocks will wait in a queue until they are cleared. If TRIM is not enabled, then these blocks will wait until the SSD's controller is able to make the time to clear these NAND blocks which usually will only happen when the SSD is idle so that the SSD's garbage collection mechanisms have time to work so as not to affect system performance. However, if there are no more empty ready to go NAND blocks, then the SSD's controller will start clearing these waiting NAND blocks which will slow down the performance of the SSD. If TRIM is enabled, then these pending NAND blocks are cleared at some earlier time.

There are actually two types of TRIM. Queued and non-queued TRIM. Non-queued TRIM support is also called periodic TRIM where the OS scans the file systems and sends a command to the SSD to immediately clear any NAND blocks not being used by the file system (this is safer since the list of blocks is created as the TRIM command is sent).

Queued TRIM is actually dangerous as it depends on both the OS file system driver and the SSD to have properly working TRIM support, but many SSDs have faulty TRIM support because it is difficult to design (I think because too many things change from the time the OS creates a list of blocks needing TRIMed and when the SSD actually performs the TRIM operation that things may have become out of sync between the queued list of blocks and the currently use/unused blocks on the SSD). Queued TRIM keeps a list of every file system operation that deletes data. Queued TRIM support relies on the OS to tell the SSD which NAND blocks have been released from file system use so if there is some miscommunication by the OS or the SSD on which blocks are which, then the SSD may end up clearing the wrong NAND block which actually contains data since so much time may have elapsed since the creation of the list of queued blocks and the time TRIM is actually activated which may have had the SSD's garbage collection doing a lot of work where maybe the blocks had already been cleared, but are cleared again because of the list created a long time ago -- so those blocks on the list are now being used for data, so there is data loss. This is why Linux does not automatically enable automatic queued TRIM support and according to this Wikipedia article both Windows and macOS utilize non-queued (aka periodic) TRIM.

https://en.wikipedia.org/wiki/Trim_(computing)#Disadvantages

General TRIM information:

https://www.crucial.com/articles/about-ssd/what-is-trim

More detailed information on TRIM and SSD's internal Garbage Collection routines:

https://arstechnica.com/gadgets/2015/04/ask-ars-my-ssd-does-garbage-collection-so-i-dont-need-trim-right/

Here is a post in the comments of the last article which mentions the difference of Queued and non-Queued TRIM:

https://arstechnica.com/gadgets/2015/04/ask-ars-my-ssd-does-garbage-collection-so-i-dont-need-trim-right/?comments=1&post=28924525

jhrichmond wrote:

So regarding the SSD in my 27"iMac: can I just check

1) Does the TRIM command you gave me enable Non-Queued TRIM and not Queued TRIM?

Non-queued TRIM according to the Wikipedia article I linked & noted in my previous post.

2) I am running Catalina 10.15.7 - will the TRIM command you gave me work on that version of OSX?

Yes. I believe it works as far back as macOS 10.13 High Sierra. I forget exactly when this command was implemented by Apple.

My SSD is a 1TB OWC Mercury Electra 6Gb/s 2.5" SSD - bought from OWC in 2019. I have contacted OWC to ask if TRIM can be enabled on this SSD but they have not yet replied. I will post their reply here when I get it, and will wait for that before enacting the TRIM command on my SSD.

On the early OWC Mercury Electra SSDs they said TRIM was not necessary (did not matter if it was enabled either). However, I recently saw another Apple forum posting with a recent model of this SSD where they were having issues and TRIM was not enabled. The later versions of this SSD uses a different SSD controller than the original early model and I don't believe their product page even mentions TRIM one way or another these days.

By the way, how does that command line know to direct the TRIM command to the correct internal SSD? (The NVME SSD seems to already have TRIM enabled; the OWC 1TB SSD does not have TRIM enabled, and I have a third SSD, an external Samsung T7 2TB SSD labeled disk 5 in the EtreCheck report and the report does not indicated if TRIM is enabled or not on that SSD. Will the TRIM command you gave me target all attached SSDs? Should I disconnect the external Samsung before issuing the TRIM command?

AFAIK TRIM support on Macs will only work on the internal SSDs. It will affect all internal SSDs which support TRIM. TRIM support for external SSDs becomes tricky because the OS must support it as well as the USB controller and enclosure used by the external SSDs. You can check the Apple System Profiler to confirm whether TRIM has been activated on the SSDs.

It is possible the hard drive is worn out or even beginning to fail. The SSD part of the Fusion Drive will hide some of this performance degradation to a point, but eventually it will no longer be able to "cover" for the slow worn out/failing hard drive.

To check the health of the hard drive run DriveDx and post the complete DriveDx text report here using the "Additional Text' icon which looks like a piece of paper. Usually any "Warning" or "Failing" notices on a hard drive indicates the hard drive is worn out or failing respectively. Sometimes the "Warning" of a worn out hard drive may not have any performance impact, but sooner or later it will. Unfortunately these types of apps don't correctly interpret the health of an SSD as it is always best to manually interpret the health information of the SSD since not all "Warning" or "Failing" notices on an SSD are a problem.

  disk1 - APPLE HDD HTS541010A9E662 1.00 TB (Mechanical - 5400 RPM

The main problem appears to be the snail like speed of your 5400 rpm drive in the21.5" . The tiny SSD helps launch apps - it does nothing for the regular read/write speeds.

The hard drive is past the manufacturer's expected lifetime of power on hours of about 47K which is extremely low for a 3.5" drive, but it does show how poorly these hard drives are made these days (years ago a standard desktop grade drive was expected to last for 80K power on hours).

While the drive may be perfectly fine yet even being past the manufacturer's life time expectations there is another health attribute that is more of a concern to me. The "Load Cycle Count" is at 14% now which is getting very low. I know when this value gets to 1% that I have encountered severe performance issues as well as some other odd behaviors. While in theory the drive should still be fully functional at this point, I would guess with both of these things combined is why you are suddenly noticing performance issues assuming nothing else on this iMac is interfering or contributing to the problem.

Like others have already noted, a spinning hard drive is always going to be slow especially with the 5,400rpm drives which Apple uses on low end models. But with age these drives do get even slower. At least you now know that your already slow hard drive is no longer healthy.

I woud never run any Mac with a 5400 rpm spinning drive - period. I bought one once and sold it three months later at a loss to get rid of it. They are entry level drives and even if you only use one app at a time, it will be slow - depending on the app, even super slow. Anything that requires a fast processor, RAM, and a fast drive will make it slow down to a crawl.

The zsh message is perfectly normal for systems that have upgraded macOS to 10.15+ from older versions of macOS. You can just ignore that message as it is only relevant to people who know how to use the command line.

As for the 24GB Apple SSD, there isn't much use for it.

Please post both EtreCheck reports, having multiple sets of eyes view them helps to ensure everything is caught.