Jernigan, Kevin wrote: >On 3/24/16, 3:09 PM, "Albe Laurenz" <laurenz.a...@wien.gv.at> wrote: >>> Disk is only a single point of failure in RAC if you configure >>> non-redundant storage. >>> In general, Oracle recommends triple mirroring to protect against disk >>> failures, >>> as they have had many experiences over the years where customers with >>> mirrored disks >>> would see consecutive disk failures within short periods of time. >> >>The single point of failure in Oracle RAC is the ASM file system. > > Only if you misconfigure ASM for RAC: with RAC, an ASM instance will run on > every RAC node, > and if the ASM instance fails on any one node, the RAC instance on that node > will go down, > but the RAC instances on the other nodes will continue to run - so the > database will remain > accessible, though with fewer processors available. > > If you configure ASM to implement at least dual mirroring for storage - and > I’m pretty sure > Oracle intentionally makes it hard to configure ASM without mirroring - then > ASM will continue > run through any single disk failure.
I think you missed my point. I am not talking about disk failure, but about some failure (possibly a software bug or a combination of hardware problem and software weakness) that causes the on-disk data to be corrupted. File system corruption. Mirroring will only mirror such a corruption, and multiple ASM instances that all access the same corrupted data won't help either. Of course Oracle says that ASM is so simple and bullet-proof that this cannot happen, but claiming that something cannot fail is not good enough. RAC is a shared storage system, and that shared storage is a single point of failure. Yours, Laurenz Albe -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
