JBOD as talked about here http://www.datastax.com/wp-content/uploads/2012/08/C2012-StateofCassandra-JonathanEllis.pdf and defined by disk_failure_policy
So that when you have very large nodes disk failed does not require a full replacement. But if you are using a high level raid guess that's not necessary. Cheers ----------------- Aaron Morton Freelance Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 2/04/2013, at 6:35 PM, "Hiller, Dean" <dean.hil...@nrel.gov> wrote: > Oh, JBOD, not JBOB. > > no, we were using RAID 5 and RAID 6 from what I understand. I am trying to > get a test run with just one disk to make sure the test is correct as one > disk should have much less performance than 20 in the case of random access. > In sequential, I think performance would be the same(ie. Both would be > 250MB/sec in throughput is my guess) > Thanks, > Dean > > From: <Hiller>, Nrel <dean.hil...@nrel.gov<mailto:dean.hil...@nrel.gov>> > Date: Tuesday, April 2, 2013 6:40 AM > To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" > <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > Subject: Re: how to test our transfer speeds > > Is 1.2 JBOB and april fools joke? Heh, seriously though, I have no idea what > you are talking about there. I am trying to get raw disk performance with no > cassandra involved before involving cassandra…..which is the next step. > > Thanks, > Dean > > From: aaron morton <aa...@thelastpickle.com<mailto:aa...@thelastpickle.com>> > Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" > <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > Date: Monday, April 1, 2013 11:01 PM > To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" > <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> > Subject: Re: how to test our transfer speeds > > If not, maybe I just generate the same 1,000,000 files on each machine, then > randomly delete 1/2 the files and stream them from the other machine as > writing those files would all be in random locations again forcing a much > worse measurement of MB/sec I would think. > Not sure I understand the question. But you could just scrub the data off a > node and rebuild it. > > Note that streaming is throttled, and it will also generate compaction. > > He has twenty 1T drives on each machine and I think he also tried with one 1T > drive seeing the same performance which makes sense if writing sequentially > Are you using the 1.2 JBOB configuration? > > Cheers > > ----------------- > Aaron Morton > Freelance Cassandra Consultant > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 1/04/2013, at 11:01 PM, "Hiller, Dean" > <dean.hil...@nrel.gov<mailto:dean.hil...@nrel.gov>> wrote: > > (we plan on running similar performance tests on cassandra but wanted to > understand the raw foot print first)….. > > Someone in ops was doing a test transferring 1T of data from one node to > another. I had a huge concern I emailed him that this could end up being a > completely sequential write not testing random access speeds. He has twenty > 1T drives on each machine and I think he also tried with one 1T drive seeing > the same performance which makes sense if writing sequentially. Does anyone > know of something that could generate a random access pattern such that we > could time that? Right now, he was measuring 253MB / second from the time > it took and the 1T of data. I would like to find the much worse case of > course. > > If not, maybe I just generate the same 1,000,000 files on each machine, then > randomly delete 1/2 the files and stream them from the other machine as > writing those files would all be in random locations again forcing a much > worse measurement of MB/sec I would think. > > Thoughts? > > Thanks, > Dean >
