Re: [Aoetools-discuss] active/active aoe + raid0
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From: Ed C. <ec...@co...> - 2009-10-15 15:19:59
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On Thu Oct 15 10:56:55 EDT 2009, ec...@co... wrote: ... > However, most of the problems I can think of with using md on two > initiators at the same time over a common set of AoE targets have to > do with failing individual components, or with the consistency of the > state of the RAID itself, and these issues go away with a RAID 0, > since it's not redundant and immediately fails when one component > fails. What am I saying? The main problem is the page cache. The I/O for the components of the RAID 0 will go through the page cache on each of the two AoE initiators, and without some way for the two hosts to make sure that the page cache contents match (e.g., "I just changed the data here---update your cache!") the scenario won't work. Because not all the data is on the md components but can also be in RAM on the host doing md RAID, you will have data corruption if you introduce a third location for data to be: the RAM of the second AoE initiator doing md. -- Ed Cashin <ec...@co...> http://www.coraid.com/ http://noserose.net/e/ |