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From Ted Yu <yuzhih...@gmail.com>
Subject Re: [In Memory] Questions about Make HBase Table In Memory
Date Mon, 24 Oct 2016 03:19:00 GMT
Puts are stored in memstore. Get / Scan would include such data in memstore
when row keys match.

For #2, see http://hbase.apache.org/book.html#block.cache.design

For #3, one indication is latency of the result. Latency would be longer
when disk is involved.

On Sun, Oct 23, 2016 at 8:01 PM, Proust(Proust/Feng Guizhou) [Saipan] ­ <
pfeng@coupang.com> wrote:

> Hi, HBase Experts
> I have several questions related to HBase BlockCache and IN_MEMORY setting
> 1. Does BlockCache cache the data when do PUT request, so next time
> GET/SCAN request against the same data will be served from Memory only?
> 2. If HBase Table ColumnFamily have *IN_MEMORY=true*, and every time I do
> PUT  followed immediately with a GET/SCAN against the same data, assume I
> have memory larger than the specific table, is that this way I can make
> sure the whole table is in memory and all read requests against this table
> will be served from memory only?
> 3. How can I determine whether a GET served from Disk Reading or Memory?
> 4. Compared to Item 2 above against "Prefetch Option for Blockcache", which
> one is best for read performance?
> The purpose I try to achieve is best and stable read performance even when
> have high HDFS IO like re-balance when new servers added. we want the
> performance could be comparable against memory solution like Redis.
> Thanks
> Proust
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