On Fri, Aug 6, 2010 at 11:32 AM, Justin Pitts <justinpitts@xxxxxxxxx> wrote: >>>> As others said, RAID6 is RAID5 + a hot spare. >>> >>> No. RAID6 is NOT RAID5 plus a hot spare. >> >> The original phrase was that RAID 6 was like RAID 5 with a hot spare >> ALREADY BUILT IN. > > Built-in, or not - it is neither. It is more than that, actually. RAID > 6 is like RAID 5 in that it uses parity for redundancy and pays a > write cost for maintaining those parity blocks, but will maintain data > integrity in the face of 2 simultaneous drive failures. Yes, I know that. I am very familiar with how RAID6 works. RAID5 with the hot spare already rebuilt / built in is a good enough answer for management where big words like parity might scare some PHBs. > In terms of storage cost, it IS like paying for RAID5 + a hot spare, > but the protection is better. > > A RAID 5 with a hot spare built in could not survive 2 simultaneous > drive failures. Exactly. Which is why I had said with the hot spare already built in / rebuilt. Geeze, pedant much? -- To understand recursion, one must first understand recursion. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
