Appreciate the insightful replies. Understood Sylvain's argument that having different partitioning locally and globally could create problem in data movement.
Edward, for a given sstable in a node, why having lexicographically closer rows clumped together should matter ? Anyways the lookups for a key in a sstable is based on sequential reads ( after first random I/O ) ? -Thanks, Prasenjit On Sat, Jul 14, 2012 at 6:58 PM, Edward Capriolo <edlinuxg...@gmail.com> wrote: > There is a more subtle and profound aspect here as well. The md5 > transformation is a hash that is good at spraying data around the hash > space evenly. For a given sstable their should be good entropy where > if the data was not transformed it could be "clumpy" and the sorted > string structure and indexes would not be as effective. > > On Sat, Jul 14, 2012 at 5:50 AM, Sylvain Lebresne <sylv...@datastax.com> > wrote: >>> Any reason rowkeys are not stored by their raws keys on a given node >>> for RP ? I understand the partitioning across nodes should be >>> randomized, but on a given node why they are sorted by hash of their >>> keys and not just by the raw keys ? >> >> All the operation that change the topology of the cluster >> (adding/removing/moving a node, but repair too) requires that we are able to >> transfer data corresponding to token ranges. If rows were ordered locally by >> their raw key rather than their token, those operation would require a node >> to >> read all it's data even to transfer a small amount of it. This would be >> highly >> inefficient. >> >> -- >> Sylvain
