hbase-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Elliott Clark <ecl...@stumbleupon.com>
Subject Re: HBase row level cache for random read
Date Mon, 20 Aug 2012 15:38:18 GMT
Also if you are trying to limit the number of blocks read on random
read work loads make sure that you have bloom filters on those tables.
 Having bloom filters turned on will limit the number of blocks that
are read into memory.

On Sat, Aug 18, 2012 at 12:33 PM, Stack <stack@duboce.net> wrote:
> On Fri, Aug 17, 2012 at 4:42 PM, Gen Liu <geliu@zynga.com> wrote:
>> I assume block cache store compressed data,
>
> Generally its not, not unless you use block encoding.
>
>> one block can hold 6 rows, but in random read, maybe 1 row is ever accessed, 5/6
of the cache space is wasted.
>> Is there a better way of caching for random read. Lower the block size to 32k or
even 16k might be a choice.
>>
>
> We don't seem to list this as an option in this section,
> http://hbase.apache.org/book.html#perf.reading, but yes, if lots of
> random reads, smaller block cache could make a difference.
>
> St.Ack

Mime
View raw message