re #1, you can try grep'ing over the Accumulo metadata table to see if
there are references to the file. It's possible that some files might be
kept around for table snapshots (but these should eventually be
compacted per Mike's point in #3, I believe).
Mike Drob wrote:
1) Is your Accumulo Garbage Collector process running? It will delete
un-referenced files.
2) I've heard it said that 200 tablets per tserver is the sweet spot,
but it depends a lot on your read and write patterns.
3)
https://accumulo.apache.org/1.7/accumulo_user_manual#_table_compaction_major_everything_idle
On Tue, Jun 7, 2016 at 4:03 PM, Andrew Hulbert <[email protected]
<mailto:[email protected]>> wrote:
Hi all,
A few questions on behavior if you have any time...
1. When looking in accumulo's HDFS directories I'm seeing a
situation where "tablets" aka "directories" for a table have more
than the default 1G split threshold worth of rfiles in them. In one
large instance, we have 400G worth of rfiles in the default_tablet
directory (a mix of A, C, and F-type rfiles). We took one of these
tables and compacted it and now there are appropriately ~1G worth of
files in HDFS. On an unrelated table we have tablets with 100+G of
bulk imported rfiles in the tablet's HDFS directory.
These seems to be common across multiple clouds. All the ingest is
done via batch writing. Is anyone aware of why this would happen or
if it is even important? Perhaps these are leftover rfiles from some
process. Their timestamps cover large date ranges.
2. There's been some discussion on the number of files per tserver
for efficiency. Are there any limits on the size of rfiles for
efficiency? For instance, I assume that compacting all the files
into a single rfile per 1G split is more efficient bc it avoids
merging (but maybe decreases concurrency). However, would it be
better to have 500 tablets per node on a table with 1G splits versus
having 50 tablets with 10G splits. Assuming HDFS and Accumulo don't
mind 10G files!
3. Is there any way to force idle tablets to actually major compact
other than the shell? Seems like it never happens.
Thanks!
Andrew
