On the local disk you have the normal RocksDB working directory consisting mainly of the SSTable files. In the checkpoint directory on distributed storage it depends on whether or not you are using incremental checkpoints. For incremental checkpoints, the files are essentially the SSTables uploaded to distributed storage (their names are changed to avoid collisions) and some files are logically shared across multiple checkpoints (not physically, i.e. you cannot simply see this sharing from the files or directories and this is done to avoid redundant duplication because SSTable files are immutable). For non-incremental checkpoints you will find files in Flink’s own checkpoint format, where each file represent a dumps of all the key/value pairs from one RocksDB instance plus some meta data.
> Am 26.04.2018 um 15:22 schrieb Chirag Dewan <chirag.dewa...@yahoo.in>: > > Wow never considered it that way. > > Thanks a lot for clarifying Stefan. > > This gives rise to another question. Whats the format of this data? Is it the > same format which is used to store checkpoints when FS state backend is used? > > Regards, > > Chirag > > Sent from Yahoo Mail on Android > <https://go.onelink.me/107872968?pid=InProduct&c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers&af_wl=ym&af_sub1=Internal&af_sub2=Global_YGrowth&af_sub3=EmailSignature> > On Thu, 26 Apr 2018 at 5:30 PM, Stefan Richter > <s.rich...@data-artisans.com> wrote: > Hi, > > I think there is a misunderstanding. RocksDB state backend always operates on > local disk of the node that runs your task to give you optimal performance. > You can think of this as a transient working area that does not require any > durability. Durability always happens through checkpoints (or savepoints) > which, in turn, go to a distributed storage. Checkpoints and checkpoints are > like a consistent moment-in-time image of the backends content and can be > used to recover under failure (checkpoints) or manually resume your job > (savepoints). > > Best, > Stefan > >> Am 26.04.2018 um 13:16 schrieb Chirag Dewan <chirag.dewa...@yahoo.in >> <mailto:chirag.dewa...@yahoo.in>>: >> >> Hi, >> >> I am working on a use case where I need to store a large amount of data in >> state. I am using RocksDB as my state backend. Now to ensure data >> replication, I want to store the RocksDB files in some distributed file >> system. >> >> From the documentation I can see that Flink recommends a list of FileSystem >> to be used for state backend. Given here : >> >> Apache Flink 1.4 Documentation: File Systems >> <https://ci.apache.org/projects/flink/flink-docs-release-1.4/ops/filesystems.html> >> >> Apache Flink 1.4 Documentation: File Systems >> >> <https://ci.apache.org/projects/flink/flink-docs-release-1.4/ops/filesystems.html> >> >> But I cannot figure out the file system for RocksDB. What are the >> recommendations for File Systems to be used with RocksDB? >> >> Thanks in advance. >> >> Regards, >> >> Chirag >> >
