The extended or streched Oracle (RAC) cluster – part 1

for part 2, click here…

First of all, both terms ‘extended’ and ‘stretched’ are used on blogs, in documentation and logfiles. I will use ‘extended’ in this one. Also, voting files are files, not disks. Oracle will store the file(s) on one of the disks within the specified diskgroup, preferable in different failgroups. Also people talk about a ‘RAC’ cluster, but an Oracle cluster can exist without RAC. RAC is the database option to run the database in a cluster on Oracle clusterware.

Sorry, no images in this blog post… only text.

When is an Oracle cluster an extended/stretched cluster?

It’s not distance. Oracle does not know if it’s in the same or different racks or buildings, divided by roads or rivers…  There is no setting ‘extended=Y’ in Oracle that it knows about being extended.

It’s the way _you_ design the storage for Oracle clusterware and ASM.

My point of view, extended is; When there is mirroring of blocks on disks and these mirrored blocks are on disks in different storage locations. Continue reading