gfs

The distributed file systems which like Google File System and Hadoop doesn't support random I/O. (It can't modify the file which were written before. Only writing and appending is possible.) Why did they design file system like this? What are the important advantages of the design? P.S I know Hadoop will support modifing the data which were written. But they said, it's performance will very not good. Why? Hadoop distributes and replicates files. Since the files are replicated, any write operation is going to have to find each replicated section across the network and update the file. This

In BigTable/GFS and Cassandra terminology, what is the definition of a SSTable? Sorted Strings Table (borrowed from google) is a file of key/value string pairs, sorted by keys "An SSTable provides a persistent,ordered immutable map from keys to values, where both keys and values are arbitrary byte strings. Operations are provided to look up the value associated with a specified key, and to iterate over all key/value pairs in a specified key range. Internally, each SSTable contains a sequence of blocks (typically each block is 64KB in size, but this is configurable). A block index (stored at

Basically whole question is in the title. I'm wondering if it's possible to append to file located on HDFS from multiple computers simultaneously? Something like storing stream of events constantly produced by multiple processes. Order is not important. I recall hearing on one of the Google tech presentations that GFS supports such append functionality but trying some limited testing with HDFS (either with regular file append() or with SequenceFile) doesn't seems to work. Thanks, I don't think that this is possible with HDFS. Even though you don't care about the order of the records, you do