February 26, 201610 yr Some interesting ideas. Summary from The Register :- http://www.theregister.co.uk/2016/02/26/google_cloud_disk_white_paper/ The whitepaper :- http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/44830.pdf
February 26, 201610 yr That's one of the weakest papers I have seen from Google. 1) new form factor - this will happen as soon as there are no more 3.5 inch bays outside the servers/data center (any day now, see 3TB 2.5 inch). 2) remove cache from drives - the cache is already getting smaller and smaller as a ratio of capacity, and as they point out it is very effective still. They want larger IOPs/blocks (#9), the drive will need to cache at least a few of those to keep the data path SAS/SATA/new free. 3) it seems they don't know the Seagate 8TB SMR, which already combines SMR with PMR (they call it CMR). 4) already solved by read racing in erasure coding. 5) host managed SMR are available. 6) see #4 7) see #4 8 ) no comment , NDA. 9) See #1 10) See #5
February 26, 201610 yr The one thing I don't think I saw mentioned was increasing the platter size. There used to be problems with high speed disks flying apart, but I understand that's been solved, with new materials. If you were to triple the platter size, there would be a huge increase in capacity (someone do the math?). The downside would be the increased head travel, but that would not matter as much for sequential access applications. The new form factor would be an issue too, but not insolvable. Possibly too expensive though (factory retooling) ...
February 26, 201610 yr The one thing I don't think I saw mentioned was increasing the platter size. There used to be problems with high speed disks flying apart, but I understand that's been solved, with new materials. If you were to triple the platter size, there would be a huge increase in capacity (someone do the math?). The downside would be the increased head travel, but that would not matter as much for sequential access applications. The new form factor would be an issue too, but not insolvable. Possibly too expensive though (factory retooling) ... That is why the paper discusses "taller" disk drives, like the taller 3TB 2.5 inch drive. They mean to use the same platters, just more of them.
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