“Trust” seems to be a recurrent theme of the OpenZFS book. Here we discuss so-called hardware RAID.
All RAID is software RAID. Your hardware RAID controller runs a custom operating system to perform RAID tasks, and in the process obscures the storage hardware from the operating system. This made sense back in the early days of widespread commercial computing, when consumer operating systems could not be trusted. Spend three seconds contemplating OS-level software RAID on Windows 3.1, and you’ll understand why hardware RAID became ubiquitous. The computing ecosystem has changed. Our operating systems have improved. Our hardware is billions of times more powerful.
ZFS is designed for direct access to the hardware. It deliberately stores critical metadata on multiple disks.…
“Trust” seems to be a recurrent theme of the OpenZFS book. Here we discuss so-called hardware RAID.
All RAID is software RAID. Your hardware RAID controller runs a custom operating system to perform RAID tasks, and in the process obscures the storage hardware from the operating system. This made sense back in the early days of widespread commercial computing, when consumer operating systems could not be trusted. Spend three seconds contemplating OS-level software RAID on Windows 3.1, and you’ll understand why hardware RAID became ubiquitous. The computing ecosystem has changed. Our operating systems have improved. Our hardware is billions of times more powerful.
ZFS is designed for direct access to the hardware. It deliberately stores critical metadata on multiple disks. It watches those disks for errors, and makes decisions based on those errors. A hardware RAID device hides all of this worrisome detail from the operating system, eliminating ZFS’ ability to heal itself. Hardware RAID presents no competing abilities.
The Sinclair ZX81 was as good as computers got.