[server] hard disk survival

i have revised my page several times on the topic of hard disk survival, originally i was using the traditional MFBF which is widely used in engineering etc

more attuned with products that have wearout however is the idea of aual failure rate, which may not be a constant

so now i show the empirical MTBF and the calculated equivalent AFR, naturally none of this is intrinsic to a spreadsheet so my worksheet had to do it the hard way

https://hardcoregames.azurewebsites.net/?p=9311

I have separated the old EIDE disks from the SATA disks as I have retired them from service, which does skew the data as I am not sure what their real service life is

already i have more than a few disks with 40,000+ operating hours