i see these claims all teh time, and the main problem for me is that this reliability is just math. it is very promising and all, but its just math.
does anyone really believe the linux kernel can deliver data with 15 9s? does anyone believe or even care that bits (erasure encoded or not) can get to an application's memory with 15 9s? at the last talk like this, i asked what the chance was that the machine room housing the disks went lights out. no one knows, but is rather more than 15 9s. the fact that this doesn't enter into any of the failure calculations show that the analysis is incomplete. having said that, erasure coding is great and should, and will, proliferate. it is not without its own costs but is a valuable component of reliable data. On Sep 15, 2013, at 7:42 AM, Adam Levin wrote: > > However, with their system, you just tell it how protected you want your > data, and it spreads it out and does the calculations for you. You give it > the number of "safety drives" you want, for example 4, and it will do it for > you. With 4, you get 15 9's of durability. You can lose 4 drives, 4 nodes, > or even 4 racks (you obviously have to have the infrastructure available to > provide this capability, but the theory is that it's just cheap disk, and the > software is doing the work). By the way, this 15 9's protection is 70% > efficient, so 1TB of raw capacity provides 700GB of usable. If you want DR, > you just geo-spread it around the country or the world. It's not full > replication, it's calculated distributed parity using the erasure coding, so > it's more efficient, but not as fast. ----------------------- Andrew Hume 949-707-1964 (VO and best) 732-420-2275 (NJ) and...@research.att.com
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