I pulled the HDD from a fusion-drive imac when it died (problem was not disk related) and need to get into it to extract some files. I have it in a SATA/USB disk enclosure plugged into my other Mac but disk utility cannot mount it - the greyed-out disk4s2. Ideas on how I can get into it would be appreciated.
Roger
iMac 27″, macOS 10.15
With a Fusion Drive, you need both the SSD and the HD since that is how the Fusion Drive works. Since you have now separated the SSD & HD by trying to only mount the HD itself, I don't think you can now access the whole Fusion Drive even if you also connected the SSD with the HD since macOS will most likely see the Fusion Drive as split.
You may be able to use a data recovery app such as Data Rescue. Maybe you can recover some files intact, but be prepared that you may only recover files without any file names.
FYI, even if the Mac won't boot, many times a Mac can be put into Target Disk Mode to access the data on the internal drive...just needs to power on (no display necessary) and have a working Thunderbolt and/or USB port.
Also, people should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data.
Try and boot from macOS recovery (cmd +R on startup) and launch disk utility there, See if you can mount it there, and perform a disk first aid
How can I access a SATA HDD from my previous iMac?
