But, I think there's a direct relation between improving performance in
large scan and memory for memstore. Until I understand, memstore just
work as cache to write operations.
On 09/04/14 23:44, Ted Yu wrote:
Didn't quite get what you mean, Asaf.
If you're talking about HBASE-5349, please read release note of HBASE-5349.
By default, memstore min/max range is initialized to memstore percent:
globalMemStorePercentMinRange = conf.getFloat(
MEMSTORE_SIZE_MIN_RANGE_KEY,
globalMemStorePercent);
globalMemStorePercentMaxRange = conf.getFloat(
MEMSTORE_SIZE_MAX_RANGE_KEY,
globalMemStorePercent);
Cheers
On Wed, Apr 9, 2014 at 3:17 PM, Asaf Mesika <[email protected]> wrote:
The Jira says it's enabled by auto. Is there an official explaining this
feature?
On Wednesday, April 9, 2014, Ted Yu <[email protected]> wrote:
Please take a look at http://www.n10k.com/blog/blockcache-101/
For D, hbase.regionserver.global.memstore.size is specified in terms of
percentage of heap. Unless you enable HBASE-5349 'Automagically tweak
global memstore and block cache sizes based on workload'
On Wed, Apr 9, 2014 at 12:24 AM, gortiz <[email protected]<javascript:;>>
wrote:
I've been reading the book definitive guide and hbase in action a
little.
I found this question from Cloudera that I'm not sure after looking
some
benchmarks and documentations from HBase. Could someone explain me a
little
about? . I think that when you do a large scan you should disable the
blockcache becuase the blocks are going to swat a lot, so you didn't
get
anything from cache, I guess you should be penalized since you're
spending
memory, calling GC and CPU with this task.
*You want to do a full table scan on your data. You decide to disable
block caching to see if this**
**improves scan performance. Will disabling block caching improve scan
performance?*
A.
No. Disabling block caching does not improve scan performance.
B.
Yes. When you disable block caching, you free up that memory for other
operations. With a full
table scan, you cannot take advantage of block caching anyway because
your
entire table won't fit
into cache.
C.
No. If you disable block caching, HBase must read each block index from
disk for each scan,
thereby decreasing scan performance.
D.
Yes. When you disable block caching, you free up memory for MemStore,
which improves,
scan performance.
--
*Guillermo Ortiz*
/Big Data Developer/
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