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From Vladimir Tretyakov <vladimir.tretya...@sematext.com>
Subject Fwd: Does 'online region merge' make regions unavailable for some time?
Date Mon, 19 Jan 2015 09:17:44 GMT
Hi, I have one question about 'online region merge' (
https://issues.apache.org/jira/browse/HBASE-7403).
How I've understood regions which will be passed to merge method will be
unavailable for some time.

That means:
1. Some data will be unavailable some time.
2. If client will try to write data to these regions it will get exceptions.

Are above sentences correct?

Somebody can estimate time which 1 and 2 will be true? Seconds, minutes or
hours? Is there any way to avoid 1 and 2?

I am asking because now we have problem during time with number of regions
(our key contains timestamp), count of regions growing constantly
(splitting) and it become a cause of performance problem with time.
For avoiding this effect we use 2 tables:
1. First table we use for writing and reading data.
2. Second we use only for reading data.

After some time we truncate second table and rotate these tables (first
become second and second become first). That allow us control count of
regions, but solution looks a bit ugly, I looked at 'online region merge',
but we can't live with restrictions I've described in first part of
question.

Can somebody help with answers?

Thx, Vladimir Tretyakov.

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