Hi Dawid,
Thanks for looking into this! I have been distracted with other work and
did not get the time I expected to work on it.
Regards,
Jerven
On 11/30/18 12:01 PM, Dawid Weiss wrote:
Just FYI: I implemented a quick and dirty PoC to see what it'd work
like. Not much of a difference on my machine (since postings merging
dominates everything else). Interesting problem how to split it up to
saturate all of available resources though (CPU and I/O).
https://issues.apache.org/jira/browse/LUCENE-8580
Dawid
On Fri, Nov 2, 2018 at 10:17 PM Dawid Weiss <dawid.we...@gmail.com> wrote:
Thanks for chipping in, Toke. A ~1TB index is impressive.
Back of the envelope says reading & writing 900GB in 8 hours is
2*900GB/(8*60*60s) = 64MB/s. I don't remember the interface for our
SSD machine, but even with SATA II this is only ~1/5th of the possible
fairly sequential IO throughput. So for us at least, NVMe drives are
not needed to have single-threaded CPU as bottleneck.
The mileage will vary depending on the CPU -- if it can merge the data
from multiple files at ones fast enough then it may theoretically
saturate the bandwidth... but I agree we also seem to be CPU bound on
these N-to-1 merges, a regular SSD is enough.
And +1 to the issue BTW.
I agree. Fine-grained granularity here would be a win even in the
regular "merge is a low-priority citizen" case. At least that's what I
tend to think. And if there are spare CPUs, the gain would be
terrific.
Dawid
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