Casey Muratori

Does anyone out there understand the decision to store ZFS uberblocks in a _continuous_ array?

@cmuratori It seems to me that is basically just asking to have that array (which will all be on one SSD page) get wiped out together.

@cmuratori Why wouldn't you store uberblocks _strided_ across the drive instead?

@cmuratori The ZFS people seem smart so I'm wondering if I'm just not getting why it's not a problem for the uberblocks to be contiguous.

@cmuratori I'm guessing uberblocks are replicated. And they are probably not striped because syncs across disks aren't transactional.

@won3d @cmuratori (2) from same link: only *1* uberblock is actually the current valid root, you don't care what's in the other 127 anyway

@nothings @won3d Yes but that's not relevant here. Since the 128 are stored together, if that sector/pagegoes they will all go.

@cmuratori @won3d But only one of them is the current root. The other 127 are stale roots, so you don't care if you lose them.