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From Andras Szerdahelyi <andras.szerdahe...@ignitionone.com>
Subject row cache re-fill very slow
Date Mon, 19 Nov 2012 14:17:48 GMT
Hey list,

i was just wondering if anyone else is experiencing very slow ( ~ 3.5 MB/sec ) re-fill of
the row cache at start up. We operate with a large row cache ( 10-15GB currently ) and we
already measure startup times in hours :-)

How is the "saved row cache file" processed? Are the cached row keys simply iterated over
and their respective rows read from SSTables - possibly creating random reads with small enough
sstable files, if the keys were not stored in a manner optimised for a quick re-fill ? - 
or is there a smarter algorithm ( i.e. scan through one sstable at a time, filter rows that
should be in row cache )  at work and this operation is purely disk i/o bound ?

( Admittedly whatever is going on is still much more preferable to starting with a cold row
cache )

thanks!
Andras



Andras Szerdahelyi
Solutions Architect, IgnitionOne | 1831 Diegem E.Mommaertslaan 20A
M: +32 493 05 50 88 | Skype: sandrew84


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