Our major problem is that every time we need to upgrade our EMC boxes or add a new EMC box we have to shut down all the attached applications. Our SAN infrastructure is one SAN cloud where all the servers are connected to disk through one huge EMC director (Connectrix).
We need to be able to upgrade or add storage with the least effect on application. Is there any specific SAN design that can help in this matter?
I'm not familiar with the details of Connectrix operations, but the only reason an application should have to be shut down is if any of the storage resources it uses are being changed. In general, if you add capacity to an existing storage volume, you need to shut down the applications on it. The reason for this is the block address structure is changing and you really don't want applications to be manipulating these blocks while the re-mapping of the address space is going on.
A storage structure for eliminating some of this is to create multiple file system mount points for different groups of applications. A single large file system will experience more upgrade interruptions than several smaller segregated file systems (mount points). That way, each individual mount point could have storage capacity added to it, while the other mount point continue to work unchanged.
However, this does not cover the possibility that internal disk resources in the Symmetrix subsystems may need to be changed also. If changes are being made to the internal disk and port resources on the sun=bsystem, the applications would need to be halted also.
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This was first published in March 2002