Tachyon should only be marginally less performant than memory_only, because we mmap the data from Tachyon's ramdisk. We do not have to, say, transfer the data over a pipe from Tachyon; we can directly read from the buffers in the same way that Shark reads from its in-memory columnar format.
On Tue, Jul 8, 2014 at 1:18 AM, qingyang li <liqingyang1...@gmail.com> wrote: > hi, when i create a table, i can point the cache strategy using > shark.cache, > i think "shark.cache=memory_only" means data are managed by spark, and > data are in the same jvm with excutor; while "shark.cache=tachyon" > means data are managed by tachyon which is off heap, and data are not in > the same jvm with excutor, so spark will load data from tachyon for each > query sql , so, is tachyon less efficient than memory_only cache strategy > ? > if yes, can we let spark load all data once from tachyon for all sql query > if i want to use tachyon cache strategy since tachyon is more HA than > memory_only ? >
