Konstantin, Could you provide me link to how this was done on a big feature, like say append and how benchmark info was captured? I am planning to run dfsio tests, btw.
Regards, Suresh On Tue, Apr 26, 2011 at 11:34 PM, suresh srinivas <srini30...@gmail.com>wrote: > Konstantin, > > On Tue, Apr 26, 2011 at 10:26 PM, Konstantin Shvachko < > shv.had...@gmail.com> wrote: > >> Suresh, Sanjay. >> >> 1. I asked for benchmarks many times over the course of different >> discussions on the topic. >> I don't see any numbers attached to jira, and I was getting the same >> response, >> Doug just got from you, guys: which is "why would the performance be >> worse". >> And this is not an argument for me. >> > > We had done testing earlier and had found that performance had not > degraded. We are waiting for out performance team to publish the official > numbers to post it to the jira. Unfortunately they are busy qualifying 2xx > releases currently. I will get the perf numbers and post them. > > >> >> 2. I assume that merging requires a vote. I am sure people who know bylaws >> better than I do will correct me if it is not true. >> Did I miss the vote? >> > > > As regards to voting, since I was not sure about the procedure, I had > consulted Owen about it. He had indicated that voting is not necessary. If > the right procedure is to call for voting, I will do so. Owen any comments? > > >> >> It feels like you are rushing this and are not doing what you would expect >> others to >> do in the same position, and what has been done in the past for such large >> projects. >> > > I am not trying to rush here and not follow the procedure required. I am > not sure about what the procedure is. Any pointers to it is appreciated. > > >> >> Thanks, >> --Konstantin >> >> >> On Tue, Apr 26, 2011 at 9:43 PM, Doug Cutting <cutt...@apache.org> wrote: >> >> > Suresh, Sanjay, >> > >> > Thank you very much for addressing my questions. >> > >> > Cheers, >> > >> > Doug >> > >> > On 04/26/2011 10:29 AM, suresh srinivas wrote: >> > > Doug, >> > > >> > > >> > >> 1. Can you please describe the significant advantages this approach >> has >> > >> over a symlink-based approach? >> > > >> > > Federation is complementary with symlink approach. You could choose to >> > > provide integrated namespace using symlinks. However, client side >> mount >> > > tables seems a better approach for many reasons: >> > > # Unlike symbolic links, client side mount tables can choose to go to >> > right >> > > namenode based on configuration. This avoids unnecessary RPCs to the >> > > namenodes to discover the targer of symlink. >> > > # The unavailability of a namenode where a symbolic link is configured >> > does >> > > not affect reaching the symlink target. >> > > # Symbolic links need not be configured on every namenode in the >> cluster >> > and >> > > future changes to symlinks need not be propagated to multiple >> namenodes. >> > In >> > > client side mount tables, this information is in a central >> configuration. >> > > >> > > If a deployment still wants to use symbolic link, federation does not >> > > preclude it. >> > > >> > >> It seems to me that one could run multiple namenodes on separate >> boxes >> > > and run multile datanode processes per storage box >> > > >> > > There are several advantages to using a single datanode: >> > > # When you have large number of namenodes (say 20), the cost of >> running >> > > separate datanodes in terms of process resources such as memory is >> huge. >> > > # The disk i/o management and storage utilization using a single >> datanode >> > is >> > > much better, as it has complete view the storage. >> > > # In the approach you are proposing, you have several clusters to >> manage. >> > > However with federation, all datanodes are in a single cluster; with >> > single >> > > configuration and operationally easier to manage. >> > > >> > >> The patch modifies much of the logic of Hadoop's central component, >> upon >> > > which the performance and reliability of most other components of the >> > > ecosystem depend. >> > > That is not true. >> > > >> > > # Namenode is mostly unchanged in this feature. >> > > # Read/write pipelines are unchanged. >> > > # The changes are mainly in datanode: >> > > #* the storage, FSDataset, Directory and Disk scanners now have >> another >> > > level to incorporate block pool ID into the hierarchy. This is not a >> > > significant change that should cause performance or stability >> concerns. >> > > #* datanodes use a separate thread per NN, just like the existing >> thread >> > > that communicates with NN. >> > > >> > >> Can you please tell me how this has been tested beyond unit tests? >> > > As regards to testing, we have passed 600+ tests. In hadoop, these >> tests >> > > are mostly integration tests and not pure unit tests. >> > > >> > > While these tests have been extensive, we have also been testing this >> > branch >> > > for last 4 months, with QA validation that reflects our production >> > > environment. We have found the system to be stable, performing well >> and >> > have >> > > not found any blockers with the branch so far. >> > > >> > > HDFS-1052 has been open more than a year now. I had also sent an email >> > about >> > > this merge around 2 months ago. There are 90 subtasks that have been >> > worked >> > > on last couple of months under HDFS-1052. Given that there was enough >> > time >> > > to ask these questions, your email a day before I am planning to merge >> > the >> > > branch into trunk seems late! >> > > >> > >> > > > > -- > Regards, > Suresh > > -- Regards, Suresh
