Cache can be bypassed under certain conditions, such as very large size write I/O. In this implementation, if the size of an I/O request exceeds the predefined size, called write aside size, writes are sent to the disk directly to reduce the impact of large writes consuming a large cache area.  Below is the excerpt from Navisphere CLI Guide Page Number: 95  -w write-aside (Dual-SP AX4-5 series running Unisphere and CX series only) write-aside specifies, in blocks, the largest write request size that will be written to cache. Write requests greater than the write-aside value are written directly to disk, bypassing write cache. Valid values are 16 through 65534. Note: Attempting to use this switch while not in Engineering Mode will result in an error message.  EXAMPLE Change LUN 3 to enable write caching and rebuild with high priority. naviseccli -h ss1_spa chglun -l 3 -c write -r high  OUTPUT There is no output. Errors are printed to stderr.
I have been reading the great EMC book "Information Storage and Management Storing, Managing..." and I want to reconcile a term I read in the book with a configuration on the Clariion.  According to the book “Write aside size” is a configurable max size of an I/O request that is allowed to write to cache before writes are sent directly to disk.  Where do I configure this for LUNs on the Clariion? If possible could you give me an example in navisphere and the navicli? I could not find anywhere to configure this setting.
“Write aside size” for LUNs on Clariion