Hi all, I would like to build a fully geo-redundant and highly available storage solution. I read a research paper that describes the architecture of the Microsoft Azure deployment (looking to hit several hundred petabytes soon). This was presented at the 23rd ACM Symposium on Operating System Principles. Information and paper here: http://blogs.msdn.com/b/windowsazure/archive/2011/11/21/windows-azure-storag e-a-highly-available-cloud-storage-service-with-strong-consistency.aspx The thing I took away from it was that Microsoft considered 3 copies locally to be the minimum number required for protection. However, they also realized that you cannot afford to scale to an Exabyte with a 3x overhead for storage. So. they have a lazy process that goes around and behind the scenes and converts objects stored with 3X redundancy to an object that is erasure coded with Reed-Solomon having a 1.3 or 1.6 overhead. At the same time, the RS coding provides a better long term availability than the 3x replication approach. Specifics of the RS coding are here (best paper award at Usenix): https://www.usenix.org/conference/usenixfederatedconferencesweek/erasure-cod ing-windows-azure-storage As far as I have found, there are two implementations of R-S coded object stores out there: Commercial - Cleversafe (http://www.cleversafe.com/) Open Source - Tahoe-LAFS (http://www.tahoe-lafs.org/) Given a certain availability metric, stronger erasure coding can make a HUGE difference in the cost of deployment. See "Erasure Coding vs Replication: A Quantitative Comparison" here: http://oceanstore.cs.berkeley.edu/publications/papers/pdf/erasure_iptps.pdf Has any thought been given to implementing stronger erasure coding in RADOS (either directly or in a lazy fashion)? Thanks in advance for any thoughts, - Steve --- Stephen Perkins NetMass Incorporated 800-731-2737 x5005 +1-972-838-1520 x5005 perkins@xxxxxxxxxxx NetMassT The safe data company. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
