Storage troubleshooting

Ordered triage

oc> lspci / usb          (controller present?)
oc> ata / ahci / nvme    (family probe output - the message names it)
oc> dskstat              (block instances registered?)
oc> lsblk                (partitions scanned?)
oc> fatstat <dev>        (BPB parse of a suspect FAT volume)
oc> fsck <dev>           (filesystem check)
oc> fatmount <dev> /mnt  (mount)
oc> fstest               (the VFS/fs assertion suite)

The classics

Symptom	Likely cause
valid FAT32 volume refused ('invalid BPB')	wrong device node, or the alignment-destroying heap regression (fixed; rerun ata_dma_test if you touched mem_heap.c)
write lost after reboot	it lived on ramfs - only /etc and mounted volumes persist
usda appears then vanishes	USB MSC detach path - usb_hotplug_test reproduces
ext4 mount of an ext2 volume	supported (ext2 is a subset); check fsck first
mkfs refuses	the literal confirm argument is required by design