> of 2-300ms for getting a single row. This seems slow, but is it unusual?
What are those numbers? 2 ms being average? 300 ms a 95th/99th percentile? A value you saw once? Yes, this *seems* slow given your row definition but without knowing what the value represents it's almost impossible to judge. I would say its not unthinkable to see that on occasion with m1.larges, EBS drives, and a high consistency request. > I don't know if storing millions of rows in 5 nodes is unusual Generally, I would say that is a pretty reasonable number but you should look at other factors to investigate read latency and measure your overall capacity. What does JVM heap memory/CPU look like (via jmx)? What does your disk and system utilization look like (good overview, particularly on iostat: <http://spyced.blogspot.com/2010/01/linux-performance-basics.html> http://spyced.blogspot.com/2010/01/linux-performance-basics.html)? Although less important as of 0.8, are you having GC problems causing long application pause times (enable the GC logs in cassandra-env)? I feel your frustration with not knowing what is 'expected' but a performance calculator seems ambitious to me because as you pointed out, there are a significant number of important and often hard to define parameters. Dan From: Ian Danforth [mailto:idanfo...@numenta.com] Sent: October-21-11 15:12 To: user@cassandra.apache.org Subject: Specific Question, General Problem All, I have a specific question which I think highlights a general problem. ===Specific Question=== I'm seeing read times of 2-300ms for getting a single row. This seems slow, but is it unusual? Stack 5 node cluster Version .86 EC2 m1large machines ebs drives for all data (I know, I know) Datamodel Millions of rows that are at most 1440 columns wide. Each column stores a single int. ===General Problem=== I don't know what 'normal' is in Cassandra. The docs use terms like 'large' or 'wide' rows, but I don't have any absolute numbers around that adjective. I don't know if storing millions of rows in 5 nodes is unusual (maybe people scale out before they get to this size). Etc. There are plenty of people here who have an idea of what's normal for their cluster, but only a very few who know what is normal for Cassandra in general. I would love, *love*, to have a document that highlighted this. Heck I'd love to help build a 'performance calculator' in which you could put in the number of nodes, and it would tell you how much data it would be reasonable to store. (Yes I know there are a ton of variables involved.) Thanks for any light that can be shed on my specific question or the general problem. Ian No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.917 / Virus Database: 271.1.1/3963 - Release Date: 10/21/11 02:34:00
