For the Mesh Extender we need physically very small USB memory sticks for the Rhizome data store.
We have had problems with these in the past: some Verbatim ones wouldn't mount reliably at boot.
So we switched to the SANDisk Cruzer Fit.
However, those drives are not without their own problems.
In fact, they have a really nasty habit of going permanently read-only under certain circumstances. This is fairly well documented on the internet, and SanDisk have known about the problem for at least a couple of years, e.g.:
It turns out that one of those circumstances is when installing a Mesh Extender upgrade bundle.
We have had two more fail within the space of an hour today, in addition to others that have failed in the past.
We have contacted SANDisk to ask if they have fixed the root problem in their later drives, and are awaiting a response. We have also got in touch with them to see about getting replacement drives. We have offered to show them our use case that triggers the units to go read-only. Right now they signs aren't good that that they will sort things out, or even honour their statutory obligations, but we will keep you posted.
In the meantime, until SanDisk asserts and we can verify that the problem with these drives has been corrected, we strongly recommend against buying any SANDisk USB memory sticks.