> > On Tue, 25 Jun 2013, James Harper <[email protected]> > wrote: > > > with 5 SAS ports, you can have 4 data disk (yes, a power of 2) and 1 > > > parity for RAID-Z1. Or you can have three data disks (NOT a power of 2) > > > and 2 parity disks for RAID-Z3. > > > > With old hardware like that I would nominate the 5th disk as a hot spare so > > on failure you have minimum "degraded" time. This assumes that ZFS can > > handle a hot spare drive. > > http://tinyurl.com/p2wckx5 > > Page 4 of the above Google Research document shows that years 2 and 3 > have > annualised failure rates just over 8% while years 4 and 5 have rates of about > 6% and 7%. So it seems that there isn't a great increase in risk as the disk > gets older. >
I don't see anywhere that you answered my question about the generation of your server, but I assumed it's a HP DL385 (and not a HP DL385 G2 or newer), which is 7-8 years old, and I can't see how you could extrapolate google's results out that far. In any case, my concern was more related to the replacement cost of a failed disk. If you plan on using the server for 3 years then with a hot spare you can take a single disk failure with no loss of redundancy or performance. Or maybe ZFS raid can handle a failure with no loss of performance? James _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
