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https://issues.apache.org/jira/browse/HBASE-14383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14746597#comment-14746597
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Enis Soztutar edited comment on HBASE-14383 at 9/16/15 12:48 AM:
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bq. Can we retire hbase.regionserver.maxlogs?
I am in favor of that, or keeping it as a safety net, but with a much higher
default (128?).
With default settings
{code}
hbase.regionserver.maxlogs=32
hbase.regionserver.hlog.blocksize=128MB
hbase.regionserver.logroll.multiplier=0.95
{code}
We can only have 32*128*0.95 = 3.9GB of WAL entries. So, if you are running
with 32GB heap and 0.4 memstore size, the memstore space is just left unused.
Also, not related to compactions, but I have seen cases where there are not
enough regions per region server to fill the whole memstore space with the
128MB flush size, a few active regions and big heaps. We do not allow a
memstore to grow beyond the flush limit to guard against long flushes and long
MTTR times. But my feeling is that, maybe we can have a dynamically adjustable
flush size taking into account a min and max flush size and delay triggering
the flush if there is more space.
was (Author: enis):
bq. Can we retire hbase.regionserver.maxlogs?
I am in favor of that, or keeping it as a safety net, but with a much higher
default (128?).
With default settings
{code}
hbase.regionserver.maxlogs=32
hbase.regionserver.hlog.blocksize=128MB
hbase.regionserver.logroll.multiplier=0.95
{code}
We can only have 32*128*0.95 = 3.9MB of WAL entries. So, if you are running
with 32GB heap and 0.4 memstore size, the memstore space is just left unused.
Also, not related to compactions, but I have seen cases where there are not
enough regions per region server to fill the whole memstore space with the
128MB flush size, a few active regions and big heaps. We do not allow a
memstore to grow beyond the flush limit to guard against long flushes and long
MTTR times. But my feeling is that, maybe we can have a dynamically adjustable
flush size taking into account a min and max flush size and delay triggering
the flush if there is more space.
> Compaction improvements
> -----------------------
>
> Key: HBASE-14383
> URL: https://issues.apache.org/jira/browse/HBASE-14383
> Project: HBase
> Issue Type: Improvement
> Reporter: Vladimir Rodionov
> Assignee: Vladimir Rodionov
> Fix For: 2.0.0
>
>
> Still major issue in many production environments. The general recommendation
> - disabling region splitting and major compactions to reduce unpredictable
> IO/CPU spikes, especially during peak times and running them manually during
> off peak times. Still do not resolve the issues completely.
> h3. Flush storms
> * rolling WAL events across cluster can be highly correlated, hence flushing
> memstores, hence triggering minor compactions, that can be promoted to major
> ones. These events are highly correlated in time if there is a balanced
> write-load on the regions in a table.
> * the same is true for memstore flushing due to periodic memstore flusher
> operation.
> Both above may produce *flush storms* which are as bad as *compaction
> storms*.
> What can be done here. We can spread these events over time by randomizing
> (with jitter) several config options:
> # hbase.regionserver.optionalcacheflushinterval
> # hbase.regionserver.flush.per.changes
> # hbase.regionserver.maxlogs
> h3. ExploringCompactionPolicy max compaction size
> One more optimization can be added to ExploringCompactionPolicy. To limit
> size of a compaction there is a config parameter one could use
> hbase.hstore.compaction.max.size. It would be nice to have two separate
> limits: for peak and off peak hours.
> h3. ExploringCompactionPolicy selection evaluation algorithm
> Too simple? Selection with more files always wins, selection of smaller size
> wins if number of files is the same.
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