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From Vladimir Rodionov <vrodio...@carrieriq.com>
Subject RE: Slow Get Performance (or how many disk I/O does it take for one non-cached read?)
Date Sun, 02 Feb 2014 07:07:25 GMT
Block size does not matter on Linux . 256KB on read prefetch (read ahead).

Best regards,
Vladimir Rodionov
Principal Platform Engineer
Carrier IQ, www.carrieriq.com
e-mail: vrodionov@carrieriq.com

From: lars hofhansl [larsh@apache.org]
Sent: Saturday, February 01, 2014 10:33 PM
To: user@hbase.apache.org
Subject: Re: Slow Get Performance (or how many disk I/O does it take for one non-cached read?)

Hmm... Interesting. I expected there to be a better improvement from smaller blocks.

So it's really just IOPS (and block size does not matter), in which case, yes, HBase checksum
will save you 50% IOPS for each data block (and since index blocks are cache) it'll save 50%
total IOPS.

 From: Jan Schellenberger <leipzig3@gmail.com>
To: user@hbase.apache.org
Sent: Saturday, February 1, 2014 9:38 PM
Subject: Re: Slow Get Performance (or how many disk I/O does it take for one non-cached read?)

I've experimented with the block size.  Here are results:
4k - 60reads/sec  - 1.2GB totalStaticIndexSize
8k - 80reads/sec  - 660MB totalStaticIndexSize
16k - 90reads/sec  - 330MB totalStaticIndexSize
and previously
64k - 80reads/sec - ~100mb totalStaticIndexSize

Also, I turned off caching and you are correct, the index blocks seem to be
cached always - the blockCachedSize grows until it reaches
totalStaticIndexSize and then stops growing.  If you turn caching on, it
will grow until the maxHeap * blockCacheSize (.4 in my case).

I saw no performance difference between caching off/on so I guess off is

Yes, I always do a major_compact before testing.

I think this probably concludes my question - I will try to upgrade to a
newer hbase version to get the CRC32/HDFS check fix and we will probably
have to evaluate SSD's.

Cheers, everyone.

View this message in context: http://apache-hbase.679495.n3.nabble.com/Slow-Get-Performance-or-how-many-disk-I-O-does-it-take-for-one-non-cached-read-tp4055545p4055582.html

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