Out of curiosity, isn't what is really happening is this "As writes keep coming in, memory fills up causing flushes to the commit log disk of the whole memtable. In a bursting scenario, writes are thus limited only by memory and cpu in short bursting cases that tend to fit in memory. In a more long window of constant writes, the writes become limited by the constant flushing to disk of the memtable"
Ie. We kind of have two scenarios in my mind if I got that right that is from my understanding that cassandra is write to memory first and asynchronously write to disk. Later, Dean From: Alex Popescu <al...@datastax.com<mailto:al...@datastax.com>> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Date: Tuesday, July 23, 2013 12:07 PM To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>> Cc: "cassandra-u...@incubator.apache.org<mailto:cassandra-u...@incubator.apache.org>" <cassandra-u...@incubator.apache.org<mailto:cassandra-u...@incubator.apache.org>> Subject: Re: Are Writes disk-bound rather than CPU-bound? I see pretty much the same formulation in the 1.2 docs, so I'm wondering what would be the best rewrite of that paragraph? On Tue, Jul 23, 2013 at 9:00 AM, hajjat <haj...@purdue.edu<mailto:haj...@purdue.edu>> wrote: On Tue, Jul 23, 2013 at 5:05 AM, aaron morton [via [hidden email]<http://user/SendEmail.jtp?type=node&node=7589248&i=0>] <[hidden email]<http://user/SendEmail.jtp?type=node&node=7589248&i=1>> wrote: “/Insert-heavy workloads will actually be CPU-bound in Cassandra before being memory-bound/” What is the source for that ? http://www.datastax.com/docs/0.8/cluster_architecture/cluster_planning This is because everything is *first *written to the commit log *on disk*. Any thoughts?? Pretty much. Cheers ----------------- Aaron Morton Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 22/07/2013, at 8:58 AM, hajjat <[hidden email]<http://user/SendEmail.jtp?type=node&node=7589236&i=0>> wrote: “/Insert-heavy workloads will actually be CPU-bound in Cassandra before being memory-bound/” However, from reading the documentation (http://www.datastax.com/docs/1.2/dml/about_writes) it seems the disk is the real bottleneck in Writes rather than the CPU. This is because everything is *first *written to the commit log *on disk*. Any thoughts?? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Are-Writes-disk-bound-rather-than-CPU-bound-tp7589191.html Sent from the [hidden email]<http://user/SendEmail.jtp?type=node&node=7589236&i=1> mailing list archive at Nabble.com<http://Nabble.com>. ________________________________ If you reply to this email, your message will be added to the discussion below: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Are-Writes-disk-bound-rather-than-CPU-bound-tp7589191p7589236.html To unsubscribe from Are Writes disk-bound rather than CPU-bound?, click here. NAML<http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> -- Mohammad Hajjat Ph.D. Student Electrical and Computer Engineering Purdue University ________________________________ View this message in context: Re: Are Writes disk-bound rather than CPU-bound?<http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Are-Writes-disk-bound-rather-than-CPU-bound-tp7589191p7589248.html> Sent from the cassandra-u...@incubator.apache.org mailing list archive<http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/> at Nabble.com. -- :- a) Alex Popescu @al3xandru
