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From Kanwar Sangha <kan...@mavenir.com>
Subject RE: Read IO
Date Thu, 21 Feb 2013 16:44:14 GMT
Ok.. Cassandra default block size is 256k ? Now say my data in the column is 4 MB.  And the
disk is giving me 4k block size random reads @ 100 IOPS. I can read max 400k in one seek ?
does that mean I would need multiple seeks to get the complete data ?


-----Original Message-----
From: scode@scode.org [mailto:scode@scode.org] On Behalf Of Peter Schuller
Sent: 21 February 2013 00:05
To: user@cassandra.apache.org
Subject: Re: Read IO

> Is this correct ?

Yes, at least under optimal conditions and assuming a reasonably sized row. Things like read-ahead
(at the kernel level) will play into it; and if your read (even if assumed to be small) straddles
two pages you might or might not take another read depending on your kernel settings (typically
trading pollution of page cache vs. number of I/O:s).

--
/ Peter Schuller (@scode, http://worldmodscode.wordpress.com)
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