Should I replicate a ReadOnly volume on the same partition and server as the ReadWrite volume?
Yes, Absolutely! It improves the robustness of your served volumes. If ReadOnly volumes exist (note use of term exist rather than are available), Cache Managers will never utilize the ReadWrite version of the volume. The only way to access the RW volume is via the “dot” path (or by special mounting). This means if all RO copies are on dead servers, are offline, are behind a network partition, etc, then clients will not be able to get the data, even if the RW version of the volume is healthy, on a healthy server and in a healthy network. However, you are very strongly encouraged to keep one RO copy of a volume on the same server and partition as the RW. There are two reasons for this: 1) The RO that is on the same server and partition as the RW is a clone (just a copy of the header – not a full copy of each file). It therefore is very small, but provides access to the same set of files that all other (full copy) ReadOnly volume do. Transarc trainers refer to this as the “cheap replica”.
