Inherited iMac + Fusion drive

[davvanc]

I am inheriting an iMac 27" with a 1TB fusion drive. I have no experience using a fusion drive, so I have some basic questions.
The iMac has High Sierra installed now, but I will probably erase the drive and install Mojave, then import my apps, etc.
1. Will the Mojave installer convert the fusion drive to APFS?
2. I may use a USB 3 drive with an SATA SSD drive installed connected via USB cable to boot and run the iMac. I assume Trim won't work on the USB drive, so should I expect a slow down in the future?
3. I have heard that Trim works on a Thunderbolt drive, but this iMac has Thunderbolt 1, not 3 or even 2, so do I have to get a cable converter to attach that Thunderbolt drive? (Don't have a Thunderbolt drive yet, but all I have seen for sale on the net say Thunderbolt 2 or 3)?
4. Does the "sudo Trimforce enable" command work on a fusion drive (this iMac has a 128GB SSD and a Seagate 1TB HD)?
Any advice appreciated.

 

[Juicy Box]

1. Will the Mojave installer convert the fusion drive to APFS?

Yes.

2. I may use a USB 3 drive with an SATA SSD drive installed connected via USB cable to boot and run the iMac. I assume Trim won't work on the USB drive, so should I expect a slow down in the future?

Yes, but probably not anything too dramatic.

I was wondering about this recently, and am curious if using the "Erase free space" option in old versions of Disk Utility would be like a temporary sudo-TRIM. Just do this when one notices slowdowns.

I have plans on testing this out one day.

3. I have heard that Trim works on a Thunderbolt drive, but this iMac has Thunderbolt 1, not 3 or even 2, so do I have to get a cable converter to attach that Thunderbolt drive? (Don't have a Thunderbolt drive yet, but all I have seen for sale on the net say Thunderbolt 2 or 3)?

TRIM does work on TB drives.

TB2 uses the same connector as TB1, so no adapter needed.

4. Does the "sudo Trimforce enable" command work on a fusion drive (this iMac has a 128GB SSD and a Seagate 1TB HD)?

Yes, but it should already be enabled by the OS automatically. You can varify this by going to "About this Mac">"System Report">"SATA"

Scroll down to "TRIM Enable" and it should say yes.

 

[Fishrrman]

My advice:

Once you have it, just leave it at High Sierra for now.
Get "your stuff" onto it -- you may have to remove the previous account first (unless you want to leave it on there). This can be done without too much trouble -- you don't even need to re-install the old OS.

Run with HS for a few months, just to "get used to things".
THEN... think about upgrading the OS.

 

[davvanc]

Yes.

Yes, but probably not anything too dramatic.

I was wondering about this recently, and am curious if using the "Erase free space" option in old versions of Disk Utility would be like a temporary sudo-TRIM. Just do this when one notices slowdowns.

I have plans on testing this out one day.



TRIM does work on TB drives.

TB2 uses the same connector as TB1, so no adapter needed.


Yes, but it should already be enabled by the OS automatically. You can varify this by going to "About this Mac">"System Report">"SATA"

Scroll down to "TRIM Enable" and it should say yes.

My advice:

Once you have it, just leave it at High Sierra for now.
Get "your stuff" onto it -- you may have to remove the previous account first (unless you want to leave it on there). This can be done without too much trouble -- you don't even need to re-install the old OS.

Run with HS for a few months, just to "get used to things".
THEN... think about upgrading the OS.

Thanks for the advice!