Dennis,  I am sorry .There is some problem with font in the above message.I am reposting it as there is no option to delete. Spare drives are configured to provide additional protection in the event of a drive failures.There are basically two types of Sparing : 1) Dynamic Sparing (Hot Spare) 2) Permanent Sparing 1) Dynamic Sparing : Its is a Temopary replacement . Dynamic spare is invoked against faulty drive and takes up the available mirror position.Data is then copied to the Hot spare(Dynamic spare)  and bad drive is made NR. When bad drive is replaced, data is copied back to new drive.Hot spare is released and is ready to be used again. 2) Permanent Sparing : Data is copied to the spare and Configuration changes are made to change the spare name to the failed volume name. When bad drive is replaced, it becomes part of the spare pool. Regards Amita
Dear All,  I found the document and mentioned about "Permanent Sparing". It can improve reliability by only copying data 'one way'.  Why it mention 'one way"?  What's different between normal spare and permanent spare?  Thank you for any input. Dennis Dai 
what is the "Permanent Sparing" function?