I just uploaded a simple spreadsheet I did in a statisics class to ftp.emc.com It is in the /incoming/jadams/RAID directory.  You can change the variables if you want.
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
data loss comparison - raid5 vs raid10 vs raid6