HDFS2 "Limit to 50-200 million files", is it really true like what MapR says?
On Sun, Jun 5, 2016 at 7:55 PM, Hayati Gonultas <[email protected]> wrote: > I forgot to mention about file system limit. > > Yes HDFS has limit, because for the performance considirations HDFS > filesystem is read from disk to RAM and rest of the work is done with RAM. > So RAM should be big enough to fit the filesystem image. But HDFS has > configuration options like har files (Hadoop Archive) to defeat these > limitations. > > On Sun, Jun 5, 2016 at 11:14 AM, Ascot Moss <[email protected]> wrote: > >> Will the the common pool of datanodes and namenode federation be a more >> effective alternative in HDFS2 than multiple clusters? >> >> On Sun, Jun 5, 2016 at 12:19 PM, daemeon reiydelle <[email protected]> >> wrote: >> >>> There are indeed many tuning points here. If the name nodes and journal >>> nodes can be larger, perhaps even bonding multiple 10gbyte nics, one can >>> easily scale. I did have one client where the file counts forced multiple >>> clusters. But we were able to differentiate by airframe types ... eg fixed >>> wing in one, rotary subsonic in another, etc. >>> >>> sent from my mobile >>> Daemeon C.M. Reiydelle >>> USA 415.501.0198 >>> London +44.0.20.8144.9872 >>> On Jun 4, 2016 2:23 PM, "Gavin Yue" <[email protected]> wrote: >>> >>>> Here is what I found on Horton website. >>>> >>>> >>>> *Namespace scalability* >>>> >>>> While HDFS cluster storage scales horizontally with the addition of >>>> datanodes, the namespace does not. Currently the namespace can only be >>>> vertically scaled on a single namenode. The namenode stores the entire >>>> file system metadata in memory. This limits the number of blocks, files, >>>> and directories supported on the file system to what can be accommodated in >>>> the memory of a single namenode. A typical large deployment at Yahoo! >>>> includes an HDFS cluster with 2700-4200 datanodes with 180 million >>>> files and blocks, and address ~25 PB of storage. At Facebook, HDFS has >>>> around 2600 nodes, 300 million files and blocks, addressing up to 60PB of >>>> storage. While these are very large systems and good enough for majority of >>>> Hadoop users, a few deployments that might want to grow even larger could >>>> find the namespace scalability limiting. >>>> >>>> >>>> >>>> On Jun 4, 2016, at 04:43, Ascot Moss <[email protected]> wrote: >>>> >>>> Hi, >>>> >>>> I read some (old?) articles from Internet about Mapr-FS vs HDFS. >>>> >>>> https://www.mapr.com/products/m5-features/no-namenode-architecture >>>> >>>> It states that HDFS Federation has >>>> >>>> a) "Multiple Single Points of Failure", is it really true? >>>> Why MapR uses HDFS but not HDFS2 in its comparison as this would lead >>>> to an unfair comparison (or even misleading comparison)? (HDFS was from >>>> Hadoop 1.x, the old generation) HDFS2 is available since 2013-10-15, there >>>> is no any Single Points of Failure in HDFS2. >>>> >>>> b) "Limit to 50-200 million files", is it really true? >>>> I have seen so many real world Hadoop Clusters with over 10PB data, >>>> some even with 150PB data. If "Limit to 50 -200 millions files" were true >>>> in HDFS2, why are there so many production Hadoop clusters in real world? >>>> how can they mange well the issue of "Limit to 50-200 million files"? For >>>> instances, the Facebook's "Like" implementation runs on HBase at Web >>>> Scale, I can image HBase generates huge number of files in Facbook's Hadoop >>>> cluster, the number of files in Facebook's Hadoop cluster should be much >>>> much bigger than 50-200 million. >>>> >>>> From my point of view, in contrast, MaprFS should have true limitation >>>> up to 1T files while HDFS2 can handle true unlimited files, please do >>>> correct me if I am wrong. >>>> >>>> c) "Performance Bottleneck", again, is it really true? >>>> MaprFS does not have namenode in order to gain file system performance. >>>> If without Namenode, MaprFS would lose Data Locality which is one of the >>>> beauties of Hadoop If Data Locality is no longer available, any big data >>>> application running on MaprFS might gain some file system performance but >>>> it would totally lose the true gain of performance from Data Locality >>>> provided by Hadoop's namenode (gain small lose big) >>>> >>>> d) "Commercial NAS required" >>>> Is there any wiki/blog/discussion about Commercial NAS on Hadoop >>>> Federation? >>>> >>>> regards >>>> >>>> >>>> >>>> >> > > > -- > Hayati Gonultas >
