Block locations are not persistent data. They are not kept any where after a namenode shuts down. Instead each datanode reports its blocks to the namenode at the startup time.
Hairong -----Original Message----- From: Taeho Kang [mailto:[EMAIL PROTECTED] Sent: Friday, October 05, 2007 12:51 AM To: [email protected] Subject: Re: Question on relocation of Hadoop cluster Thanks again for your answer, Raghu. Now, just out of my curiosity.... How are the exact locations of blocks/chunks being kept track of? Is there any other mechanism/information that the namenode uses, other than ip address or hostname, to manage the whereabouts of data blocks? On 10/5/07, Raghu Angadi <[EMAIL PROTECTED]> wrote: > > > (I am not sure if I replied already...) > > Taeho Kang wrote: > > Thanks for your quick reply, Raghu. > > > > The problem I am faced with is... > > - I need to move my machines to a new location > > Assuming this goes well (i.e. no data loss), > > > - The new location will assign new ip addresses for my machines. > > I am worried that this change of ip addresses may create havoc in > > the > file > > system ( i.e. discrepancy in file block info) once the cluster > > starts up > in > > the new location. > > this not an issue. > > > Is it going to be a problem? > > I don't think so. > > Raghu. > -- Taeho Kang [tkang.blogspot.com] Software Engineer, NHN Corporation, Korea
