Hello,

Does anyone have any information on estimating potential data loss chances due to raid group failure depending on raid type?  I'm putting together a detailed case for converting from heavy raid10 usage to raid5/6.  The IO considerations, performance, etc. are collected, but the general statement 'lack of redundancy' defined by a quick google search by the business I support needs to be addressed.  Especially with the concern about losing an entire vp pool with such a failure.

ie

25 x 3+1 R5 groups of 300GB FC drives in a virtual pool have a .005% chance to have a double disk failure within the same raid group vs .0008% chance for a virtual pool consisting of 50 x 2-way mirrors of 300GB FC drives.

I've read many articles, and even used the MTTDLcalc spreadsheet (how do you set rg size?  Is the percentage predicting a single disk or double disk failure? If I specify 300 drives in my array it predicts a 50% chance of data loss in the first year which doesn't seem correct) floating around the Internet, but can't seem to find a definitive answer.  Has anyone else dealt with this?

Thanks!

Scott