@Rahul : Yes. distcp can do that. And, bigger the files lesser the metadata hence lesser memory consumption.
Warm Regards, Tariq cloudfront.blogspot.com On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee < [email protected]> wrote: > IMHO,I think the statement about NN with regard to block metadata is more > like a general statement. Even if you put lots of small files of combined > size 10 TB , you need to have a capable NN. > > can disct cp be used to copy local - to - hdfs ? > > Thanks, > Rahul > > > On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <[email protected]>wrote: > >> absolutely rite Mohammad >> >> >> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[email protected]>wrote: >> >>> Sorry for barging in guys. I think Nitin is talking about this : >>> >>> Every file and block in HDFS is treated as an object and for each object >>> around 200B of metadata get created. So the NN should be powerful enough to >>> handle that much metadata, since it is going to be in-memory. Actually >>> memory is the most important metric when it comes to NN. >>> >>> Am I correct @Nitin? >>> >>> @Thoihen : As Nitin has said, when you talk about that much data you >>> don't actually just do a "put". You could use something like "distcp" for >>> parallel copying. A better approach would be to use a data aggregation tool >>> like Flume or Chukwa, as Nitin has already pointed. Facebook uses their own >>> data aggregation tool, called Scribe for this purpose. >>> >>> Warm Regards, >>> Tariq >>> cloudfront.blogspot.com >>> >>> >>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <[email protected]>wrote: >>> >>>> NN would still be in picture because it will be writing a lot of meta >>>> data for each individual file. so you will need a NN capable enough which >>>> can store the metadata for your entire dataset. Data will never go to NN >>>> but lot of metadata about data will be on NN so its always good idea to >>>> have a strong NN. >>>> >>>> >>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee < >>>> [email protected]> wrote: >>>> >>>>> @Nitin , parallel dfs to write to hdfs is great , but could not >>>>> understand the meaning of capable NN. As I know , the NN would not be a >>>>> part of the actual data write pipeline , means that the data would not >>>>> travel through the NN , the dfs would contact the NN from time to time to >>>>> get locations of DN as where to store the data blocks. >>>>> >>>>> Thanks, >>>>> Rahul >>>>> >>>>> >>>>> >>>>> On Sat, May 11, 2013 at 4:54 PM, Nitin Pawar >>>>> <[email protected]>wrote: >>>>> >>>>>> is it safe? .. there is no direct answer yes or no >>>>>> >>>>>> when you say , you have files worth 10TB files and you want to upload >>>>>> to HDFS, several factors come into picture >>>>>> >>>>>> 1) Is the machine in the same network as your hadoop cluster? >>>>>> 2) If there guarantee that network will not go down? >>>>>> >>>>>> and Most importantly I assume that you have a capable hadoop cluster. >>>>>> By that I mean you have a capable namenode. >>>>>> >>>>>> I would definitely not write files sequentially in HDFS. I would >>>>>> prefer to write files in parallel to hdfs to utilize the DFS write >>>>>> features >>>>>> to speed up the process. >>>>>> you can hdfs put command in parallel manner and in my experience it >>>>>> has not failed when we write a lot of data. >>>>>> >>>>>> >>>>>> On Sat, May 11, 2013 at 4:38 PM, maisnam ns <[email protected]>wrote: >>>>>> >>>>>>> @Nitin Pawar , thanks for clearing my doubts . >>>>>>> >>>>>>> But I have one more question , say I have 10 TB data in the pipeline >>>>>>> . >>>>>>> >>>>>>> Is it perfectly OK to use hadopo fs put command to upload these >>>>>>> files of size 10 TB and is there any limit to the file size using >>>>>>> hadoop >>>>>>> command line . Can hadoop put command line work with huge data. >>>>>>> >>>>>>> Thanks in advance >>>>>>> >>>>>>> >>>>>>> On Sat, May 11, 2013 at 4:24 PM, Nitin Pawar < >>>>>>> [email protected]> wrote: >>>>>>> >>>>>>>> first of all .. most of the companies do not get 100 PB of data in >>>>>>>> one go. Its an accumulating process and most of the companies do have a >>>>>>>> data pipeline in place where the data is written to hdfs on a frequency >>>>>>>> basis and then its retained on hdfs for some duration as per needed >>>>>>>> and >>>>>>>> from there its sent to archivers or deleted. >>>>>>>> >>>>>>>> For data management products, you can look at falcon which is open >>>>>>>> sourced by inmobi along with hortonworks. >>>>>>>> >>>>>>>> In any case, if you want to write files to hdfs there are few >>>>>>>> options available to you >>>>>>>> 1) Write your dfs client which writes to dfs >>>>>>>> 2) use hdfs proxy >>>>>>>> 3) there is webhdfs >>>>>>>> 4) command line hdfs >>>>>>>> 5) data collection tools come with support to write to hdfs like >>>>>>>> flume etc >>>>>>>> >>>>>>>> >>>>>>>> On Sat, May 11, 2013 at 4:19 PM, Thoihen Maibam < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>>> Hi All, >>>>>>>>> >>>>>>>>> Can anyone help me know how does companies like Facebook ,Yahoo >>>>>>>>> etc upload bulk files say to the tune of 100 petabytes to Hadoop HDFS >>>>>>>>> cluster for processing >>>>>>>>> and after processing how they download those files from HDFS to >>>>>>>>> local file system. >>>>>>>>> >>>>>>>>> I don't think they might be using the command line hadoop fs put >>>>>>>>> to upload files as it would take too long or do they divide say 10 >>>>>>>>> parts >>>>>>>>> each 10 petabytes and compress and use the command line hadoop fs put >>>>>>>>> >>>>>>>>> Or if they use any tool to upload huge files. >>>>>>>>> >>>>>>>>> Please help me . >>>>>>>>> >>>>>>>>> Thanks >>>>>>>>> thoihen >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> Nitin Pawar >>>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> Nitin Pawar >>>>>> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Nitin Pawar >>>> >>> >>> >> >> >> -- >> Nitin Pawar >> > >
