"Michael Stone" <[EMAIL PROTECTED]> writes: "Michael Stone" <[EMAIL PROTECTED]> writes:
> On Wed, May 30, 2007 at 07:06:54AM -0700, Luke Lonergan wrote: > > > Much better to get a RAID system that checksums blocks so that "good" is > > known. Solaris ZFS does that, as do high end systems from EMC and HDS. > > I don't see how that's better at all; in fact, it reduces to exactly the same > problem: given two pieces of data which disagree, which is right? Well, the one where the checksum is correct. In practice I've never seen a RAID failure due to outright bad data. In my experience when a drive goes bad it goes really bad and you can't read the block at all without i/o errors. In every case where I've seen bad data it was due to bad memory (in one case bad memory in the RAID controller cache -- that was hell to track down). Checksums aren't even enough in that case as you'll happily generate a checksum for the bad data before storing it... -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
