rvp Writes to MS-DOS filesystems are slower than writes to the native UFS.
It's just stalls completely, command couldn't be interrupted with Ctrl+C, couldn't be killed via kill -TERM <process_id> or even via kill -KILL <process_id>, samba’s share couldn’t be accessed via network during those stalls.
rvp Or, it could be the USB-stick firmware doing block remapping (USB write speeds can vary quite a bit when this is happening)
Today I copied files to a new drive with ffs on it from an old SSD-drive with NTFS filesystem mounted through FUSE ntfs-3g(PERFUSE_BUFSIZE=135168 was set) and experienced preasumbly same behavior, after that I’ve remounted it through built-in NTFS kernel module and everything has copied OK. In the first case cp twice(!!!) has copied only first file and stalled around 14MB mark, with built-in module I’ve copied over 50GB
rvp BTW, what cluster size did newfs_msdos report when you formatted the drive?.
Sorry, I do not remember, it was the default for an 8GB stick, I had only used -F 32 and -L options. If it’s important I could check it.