Well, technically, 1st_arrival_time is O(number of network hops between racks) which is O(#racks) and obviously #racks is a function of the number of datanodes. But you're talking an extra 0.1ms or so there per network hop, and there isn't any system which could avoid it.
But HDFS-wise, the data structures are mostly hashtable based. -Todd On Thu, Jan 6, 2011 at 2:01 AM, KevinKuei <kk...@above.net.tw> wrote: > Dear Todd, > > Thanks for your reply. > Let me clarify my "response time" definition. > > *start_time: time of request send > *1st_arrival_time: the 1st block of data been received > *completed_time: the final block of data been received > > response time = 1st_arrival_time = start_time > > Are you still confirmed that there is NO "response_time = O(number of > datanode)" ? > If so, HDFS will be great for our application. Thanks!! > > > -- > Kevin Kuei > > > 於 2011/1/6 下午 04:23, Todd Lipcon 提到: > > Hi Kevin, > > No, there is no O(number of datanodes) factor in performance. > > -Todd > > On Wed, Jan 5, 2011 at 8:04 PM, KevinKuei <kk...@above.net.tw> wrote: > >> Hi, >> >> I'm planing for a youtube-like video online site and looking for a >> suitable file system. >> The high performance and reliability of HDFS seems to be the great >> candidate. >> >> But somebody told me that the response time will be linear increased with >> more data node. >> I've no enough hardwares to do the test for now. >> >> It will be very appreciated if anyone can provide such information. >> >> Thanks!! >> >> -- >> Kevin Kuei >> >> -- >> This message has been scanned for viruses and >> dangerous content by MailScanner, and is >> believed to be clean. >> >> > > > -- > Todd Lipcon > Software Engineer, Cloudera > > -- > This message has been scanned for viruses and > dangerous content by *MailScanner* <http://www.mailscanner.info/>, and is > believed to be clean. > > > > -- > This message has been scanned for viruses and > dangerous content by *MailScanner* <http://www.mailscanner.info/>, and is > believed to be clean. > -- Todd Lipcon Software Engineer, Cloudera
