IMHO this is a spectacularly bad idea. Is it a one off event? Why not just take the perf hit and recreate the file?
If you need to do this regularly you should consider a mutable file store like HBase. If you start modifying blocks from under HDFS you open up all sorts of consistency issues. On Fri, Jul 18, 2014 at 2:10 PM, Shumin Guo <[email protected]> wrote: > That will break the consistency of the file system, but it doesn't hurt to > try. > On Jul 17, 2014 8:48 PM, "Zesheng Wu" <[email protected]> wrote: > >> How about write a new block with new checksum file, and replace the old >> block file and checksum file both? >> >> >> 2014-07-17 19:34 GMT+08:00 Wellington Chevreuil < >> [email protected]>: >> >>> Hi, >>> >>> there's no way to do that, as HDFS does not provide file updates >>> features. You'll need to write a new file with the changes. >>> >>> Notice that even if you manage to find the physical block replica files >>> on the disk, corresponding to the part of the file you want to change, you >>> can't simply update it manually, as this would give a different checksum, >>> making HDFS mark such blocks as corrupt. >>> >>> Regards, >>> Wellington. >>> >>> >>> >>> On 17 Jul 2014, at 10:50, Zesheng Wu <[email protected]> wrote: >>> >>> > Hi guys, >>> > >>> > I recently encounter a scenario which needs to replace an exist block >>> with a newly written block >>> > The most straightforward way to finish may be like this: >>> > Suppose the original file is A, and we write a new file B which is >>> composed by the new data blocks, then we merge A and B to C which is the >>> file we wanted >>> > The obvious shortcoming of this method is wasting of network bandwidth >>> > >>> > I'm wondering whether there is a way to replace the old block by the >>> new block directly. >>> > Any thoughts? >>> > >>> > -- >>> > Best Wishes! >>> > >>> > Yours, Zesheng >>> >>> >> >> >> -- >> Best Wishes! >> >> Yours, Zesheng >> > -- CONFIDENTIALITY NOTICE NOTICE: This message is intended for the use of the individual or entity to which it is addressed and may contain information that is confidential, privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that any printing, copying, dissemination, distribution, disclosure or forwarding of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and delete it from your system. Thank You.
