Method and apparatus for immunizing applications on a host server from failover processing within a switch
View Patent ↗A method and apparatus for providing host server immunization from a failover process that may occur within a data switch that couples the host server to a storage volume. To facilitate such immunization, the method and apparatus caches non-read/write information that is generated by the switch during initialization of the storage volume to host server communication. Upon failover of a switch component within a failover pair of switch components in the switch, the read/write requests issued by the server are ignored and any non-read/write information commands are responded to using the cached information.
1. A method for immunizing applications on a host server from a switch component failover comprising:
beginning a switch component failover process;
ignoring a read/write request issued by the host server;
responding to a non-read/write information command using cached information;
upon initialization of a switch component, caching any non-read/write information delivered to the host server during initialization; and
when the switch component failover process is complete, responding to read/write requests.
2. The method of claim 1 wherein the cached information is stored within at least one switch component in a plurality of switch components.
3. The method of claim 1 wherein the cached information is cached in memory of at least one pair of switch components.
4. The method of claim 1 wherein the host server waits a predefined period between issuing a read/write request and issuing a non-read/write information command.
5. The method of claim 1 wherein the non-read/write information command comprises a logical unit number identification command.
6. The method of claim 1 wherein the non-read/write information command comprises at least one of an inquiry command, a test unit ready command, a read capacity command, or a mode sense command.
7. The method of claim 1 wherein the switch component is a virtualization card.
8. Apparatus for immunizing applications on a host server from a switch component failover comprising:
a volume manager for detecting a switch component failure and, upon such a failure, ignoring any read/write request issued by the host server; and
a cache memory, controlled by the volume manager, for supplying cached non-read/write information whenever the host server issues a non-read/write information command and, upon initialization of a switch component, caching any non-read/write information delivered to the host server during initialization.
9. The apparatus of claim 8 wherein the cached information is stored within at least one switch component in a plurality of switch components.
10. The apparatus of claim 8 wherein the non-read/write information is cached in memory of at least one pair of switch components.
11. The apparatus of claim 8 wherein the host server waits a predefined period between issuing a read/write request and issuing a non-read/write information command.
12. The apparatus of claim 8 wherein the non-read/write information command comprises a logical unit number identification command.
13. The apparatus of claim 8 wherein the non-read/write information command comprises at least one of an inquiry command, a test unit ready command, a read capacity command, or a mode sense command.
14. The apparatus of claim 8 wherein the switch component is a virtualization card.