RAID references that I find useful

I am keeping it simple – this is reference that helps me explain things for myself and for my customers. Situation: why do I need RAID 5 when we have 2 NAS’s – it already has redundancy/backup. RAID 5 is not being used for redundancy – it is used to lower the overall cost of a system you know WILL fail 1 day (these hard drive are quite hot and are mechanical devices)

• Raid Calculator
• Types of RAID explained
  

• Best Types of Server Drives (results over the past year – Jan 2018-2019)
  • so if a 25% loss of drive space is created by RAID 5 – buy a drive 25% larger – so eg. 10TBx4 = 30TB (assuming RAID 5) – simply buy 14TBx4 drives which makes makes it a 30TB drive, buy 14TBx4 = 42TB (assuming RAID 5).
  • well that is a stupid and obvious argument! (you might say) … well until $$ is considered. The diff in price between 4x10TB and 4x14TB server class drives is $70×4 = $240.
    • if a drive fails – you ideally should be able to pop in another one and the system should rebuild it self (I have been through this with 4 failed drives over 1 month with RAID 10 (double RAID5-ish) and it is the coolest thing to see work!
    • An assumption in this argument was that there were 2 mirrored NAS’s – providing the redundancy
    • How long $$-wise would it take your IT guy to rebuild a new unit. If it is cheaper than the larger drives – don’t use RAID. Note that that was a facetious comment. It would take at least 6 hours to get everything back up and mirrored from the NAS in another location.
    • So RAID 5 in this case has NOTHING to do with data redundancy but everything to do with “how fast can I get a broken hard drive up and running on the NAS” AND how much down time I will NOT be spending on hardware fixing (same reason people buy Toyota/Honda’s)
    • RAID 5 should also allow 1 drive to fail and the NAS still would be working.

Does higher temp decrease the life!? Yes it does – the theory hasn’t changed since my days at the Uni. But … it is all in context. If the drive manufacturer did a good job and cooling is adequate then … lets see some empiric evidence (note the WD has the longest lasting drives). This guy totally disagrees with the theory (I am arguing that)– BUT … the manufacturers and the environment the drives are in are likely well built – so it is a whole system.

AFK vs. MTBF Use AFK for hard drives is a suggestoin by Seagate.