I bought a NVMe SSD after reading about how fast they were and hoped to achieve a bootable Monterey backup for my iMac. The photos on Amazon had not prepared me for how tiny this storage is. It's a 1 Tb SSD that I formatted in APFS with three volumes: a Monterey backup, a Mojave backup (which is bootable) and a data volume all in an enclosure not much bigger than my thumb. I was surprised to see the measurements of space remaining pertains to the whole drive, not the individual volumes. I guess the volumes/partitions have flexible borders to accommodate needs. Clever.
Do not confuse partitions and volumes. A partition is a fixed allocation of hardware
storage space. Every drive has at least one partition. A volume is a logical
grouping of data anywhere on the storage media. I HFS+ (Mac OS Extended) there is one volume per partition so they are essentially synonymous. In APFS, volumes are virtual
as they do not occupy a specific hardware location and there may be multiple volumes on the same physical partition and a volume may in turn contain sub-volumes. It is not that volumes have flexible borders as much as they have no boundaries other than those of the partition in which it exists. Volumes are roughly analogous to super folders that mount
One surprise is that DriveDX will not see the NVMe drive. I have an app called iStat Menus that can see all drives and all the parts of the Monterey drives (iMac HD, iMac HD - Data, Preboot, VM, Update) but apparently, SMART status is not supported on the NVMe drive. Disk Utility says SMART status is not supported, although is supported on the internal startup NVMe SSD. Does anyone know the best way to keep tabs on the "health" of this SSD?
I have three NVME drives, two are connected via Thunderbolt and the third is connected via USB. Thunderbolt standards support reporting S.M.A.R.T. but there is no provision in USB to support S.M.A.R.T. reporting, but DriveDX has no problem reporting the NVME values of all three, but it did install a helper
app that "tricks" USB into carrying the S.M.A.R.T. data. Technically NVME drives do not support S.M.A.R.T. per. se.
but do report NVME values that are roughly similar. IIRC, I did have to swap the old USB cable with a Thunderbolt 4 cable with a port adaptor before it all worked.