Ah that's a very interesting suggestion. Thank you.
The problem I have is an agonisingly slow start up from the iMac - it can take up to 30 minutes before the system restarts and all applications are responsive. Once everything is loaded the computer is pretty responsive - it is just the extraordinary restart time that is driving me crazy. Apple Support are a bit stuck on this and I don't know if it is a software problem - I have done clean installs of the most recent version of Monterey (I don't want to upgrade any further at the moment). The internal fusion drive is 1TB and still has over 400GB of storage available. I have 40GB of memory installed but from time to time things hang and I need to restart. Apple Support are stuck on the problem and I have reinstalled a fresh copy of Monterery with no real improvement. Weirdly Apple Support got me to make a new test account and that started up much faster than my own account.
So your suggestion is interesting. The 2TB Thunderblade would presumably allow me to install the system software and all apps on it including my Lightroom Catalog, boot from it and allow sufficient space for working photos. Essentially I would just ignore the internal drive since the external drives work fine for the stored photos and backups.
As you say the 5k retina screen is all that I really need. so any thoughts if that idea would work?
Philip
Your mac has thunderbolt 3- a very fast interface.
You could buy a fast PCI-harddisk connected to that interface and use it as your default workspace.
your mac-drive you can use just to startup + programs - after that don't put your photos in the home folder for that is the weak link.
You can buy something like this:
https://eshop.macsales.com/shop/owc-thunderbladeor less expensive - slower, but with more space:
https://eshop.macsales.com/shop/thunderbay-4-mini/thunderbolt-3Cheaper options are available in the Windows camp...
All you have to do is format the drive and use it as your work space.
(this drive will be useful also with future macs - then buy it large enough like 4TB and larger)
it will be a lot faster. ( your old harddrive in the mac can do 100-200MB/sec - this will do at least 1500 MB/sec)
Another thing is to buy some ram and put it into the machine to speed things up.
Don't know how much ram you have but 16 is a minimum.
They don't make these 27 inch iMacs anymore and the screen is gorgeous...
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