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From Sergey Sova <sergey.sov...@gmail.com>
Subject Can't improve low random-read speed
Date Fri, 16 Mar 2018 15:36:41 GMT
Hi. I'm investigating an issue with low random read speed for a few days,
still stuck. I've already read a few mailing list threads, didn't help,
though setup is a bit different.

HBase setup:
3 nodes, 8GB Heap for Region servers, 1 master
Table with pre-splitted 120 regions (partitioning), ~ 120M rows.
Each row has 2CF, one contains data varying 50KB - 4MB, one is smaller,
maybe around 10KB, rows can differ significantly in size, both have GZ
compression type, block size 1.3MB and 32KB respectively.
HDD disks with raid 1, 3TB SATA  6Gb/sec 7200 RPM enterprise
Network speed between nodes is 1Gbit/sec

Access pattern: get 50 random rows at once.

I run tests in 10 threads from a single application, testing both column
families, doing in total ~ 200 requests, ~20 per thread.
Bigger CF takes more time to load, don't see other differences.

Results for big CF:

Loaded data in 102 sec
Received 341065 KB  (341 MB)
Bandwidth: 3340 KB/Sec
Avg time: 7234 ms

If I perform scan (caching=100) over this table from local machine, I get
these results
Read 10000 items total
Finished in 94162 ms
KBytes read: 199451
Avg speed: 2117 KB/s
Not sure if they can help, because it's a different load pattern, but maybe
it clarifies anything.
For me, it looks strange that speed is as low as random reads.

What are my thoughts:
1. access pattern is not good for HDD - 50 random reads at once, in 10
threads, but I can't say for sure how bad is it
2. row size is rather big. I've read several posts about same problems, all
had small rows. General advice was to play with block size so HBase
wouldn't read too much data from disk, I think it's not my case.

Other observations: RegionServer gc logs look OK, RegionServer CPU
profiling does not show anything strange.

So, can someone give some hints or directions?
Thanks in advance.

Sergey

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