[Gllug] Battery-backed SAS controllers

James Hawtin oolon at ankh.org
Tue Dec 15 17:53:03 UTC 2009

On Tue, Dec 15, 2009 at 01:31:38PM +0000, Peter Corlett wrote:
> Battery-backed JBOD isn't *that* odd a requirement. ZFS is more robust  
> than hardware RAID, so there's little need to have (and pay for) the  
> extra complexity. Controller manufacturers seem to be missing a trick  
> here.

Perhaps... can you set drive timeouts for non responsing devices? Anything
but mirroring is a nightmare on non hardware based system as they may
require alot more reading to keep the parity in sync.

For an N+1 raid system you need up to N-1 reads and 2 writes for every one
real write, all that additional IO is going though your computers
kernel.... Bad!

Does ZFS do pre-emptive reads checks for failure? My hardware system does,
so ZFS check the status of drives (smart etc), for drives getting to the end
of their service life, and pre-emptively move the data to another drive
before failure, So no parity rebuild is required? My hardware system does!

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