Other What does Mode indicate on a storage device in geom output?

[puppydog]

I have a server with two nvme disks of the same model. When I run geom disk list I get the following (with lunid and ident redacted slightly):

root@server:~ # geom disk list
Geom name: nvd0
Providers:
1. Name: nvd0
   Mediasize: 512110190592 (477G)
   Sectorsize: 512
   Mode: r3w3e7
   descr: SAMSUNG MZVL2512HCJQ-00B00
   lunid: 002538bxxxxxxx
   ident: S675NX1T1xxxxx
   rotationrate: 0
   fwsectors: 0
   fwheads: 0

Geom name: nvd1
Providers:
1. Name: nvd1
   Mediasize: 512110190592 (477G)
   Sectorsize: 512
   Mode: r2w2e4
   descr: SAMSUNG MZVL2512HCJQ-00B00
   lunid: 002538bxxxxxxx
   ident: S675NX1T1xxxxx
   rotationrate: 0
   fwsectors: 0
   fwheads: 0

They're the same model of disk, formatted in zfs as a mirrored pair. Why is the mode different between the two? What does it even represent?

 

[yuripv79]

Now do a geom part list on both, there should be a difference in how some of the partitions are used. r/w/e is read-write-exclusive access, respectively.

If I had to guess, nvd0 has 3 partitions (r3w3) and nvd1 has 2 partitions (r2w2); exclusive access is even more arcane than that.