I would like to ask for a vote on whether or not to commit the cache
partition size patch (+1, -1, 0).
Background:
In the current cache, the disk is broken up into 8GB partitions where
- objects are hashed to partitions
- an object must fit entirely in a partition effectively limiting
object size and
introducing potential competition
- each partition has it's own write pointer, resulting in lots of
seeks on large
disks to write in different places
The patch adds:
- support of partitions up to .5PB (500TB) with the default 512 block
size
- larger aggregation buffer: 2MB (since we have fewer we can have
larger ones)
- larger top fast IOBuffer size (64kB), this should probably be
increased but this
patch fixes bugs which prevent increasing this in the current code
- internal cache support for large objects (still requires
VIO/IOBuffer changes + HTTP changes)
- experimental support for do_io_pread
- new on disk format which will support do_io_pread as well as
non-HTTP header access
Potential downsize:
This patch changes the on disk format which will require a cache wipe.
I have tried to include all the changes necessary to implement large
object,
pread and pluggable-protocol header usage, but one can never be sure.
The patch is available for under TS-46 in jira.
Thank you,
john
