Hi,

I am considering about protection level of a new H500 with 4 nodes, 480TB.
How difference between protection level +2d:1n and +4d:1n?
Administration guide says [+2d:1n] is 6 + 2 (25%) and [+4d:1n] is 12 + 4 (25%).

Requested protection disk space usage
http://doc.isilon.com/onefs/9.0.0/help/en-us/GUID-CA694952-948F-4740-A174-E80D22516782.html

Does it mean parity overhead with +2d:1n and +4d:1n are as same as 25%?
And does same overhead mean both +2d:1n and +4d:1n have same 324 TiB usable space?
If so, +4d:1n seems to be better than +2d:1n because 2 more disk is okay to fail.

Regards,

YASU