Hi Antonio  Thanks for your answer I clarify the concept @ and I understand the concept  but If I drill down the concept of stripe unit My 1MB file,  will It divide in 8 unit stripe 1MB/128KB =almost 8 unit stripe I have a N+1 protection could I get 2  unit stripe more by the parity? So Do I have 10 unit stripe in total?  Thanks
Hi Everyone  I am studing about overhead In the book  I saw this example 1 MB file @ 4+1  (5 node cluster)  data blocks               Metadata mirroring                    mirroring 128 * 8KB blocks @ 5/4 + (512 @ 2X)  = 1.251 MB file  1.- What is the meaning of @?  2.-How do I get the value 1.251MB  Because I get a 1MB file, I divide the 1MB between 128, because the stripe unit in the Isilon is 128 the value is 7.8  almost 8  I got the 8 stripe unit  I suppose that I get 2 stripe unit more by parity, If I distribute the unit stripe in the nodes  Could you help to get the overhead? Is correct my idea?  Thanks
file protection overhead