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From Amit Jain <jamit0...@gmail.com>
Subject Re: Help with continuous loading configuration
Date Thu, 17 Nov 2011 00:09:25 GMT
Hi Stack,

Thanks for the feedback.  Comments inline ...

On Wed, Nov 16, 2011 at 3:35 PM, Stack <stack@duboce.net> wrote:

> On Wed, Nov 16, 2011 at 3:26 PM, Amit Jain <jamit0574@gmail.com> wrote:
> > Hi Lars,
> >
> > The keys are arriving in random order.  The HBase monitoring page shows
> > evenly distributed load across all of the region servers.
>
> What kind of ops rates are you seeing?  They are running nice and
> smooth across all servers?   No stuttering?   Whats your regionserver
> logs look like?
>
> Are you presplitting your table or just letting hbase run and do up the
> splits?
>

As far as I can tell, the operations look smooth across all servers.  We're
not doing any pre-splitting, just letting HBase do the splits.


> >  I didn't see
> > anything weird in the gc logs, no mention of any failures.  I'm a little
> > unclear about what the optimal values for the following properties should
> > be:
> >
> > hbase.hstore.compactionThreshold
>
> Default is 3.  Look in regionserver logs.  See how many files you have
> on average by region columnfamily (you could also look in filesystem).
>  Are we constantly rewriting them?   If write only load mostly, you
> might up this putting off compactions till more files around (but
> looking in regionserver logs, if high write rate, we might be having
> trouble keeping up with this default threshold anyways?).
>

Well, it looks like half of the regions are in the 25-32 file range and the
other half just have 1 or 2 files.  This was when we ran it with a
compactionThreshold of 15.

How can I tell by looking at the region server logs if we're seeing a "high
write rate" ?  We've got 48 clients sending load, 12 region servers total.
 We're pushing the system pretty hard.


> > hbase.hstore.blockingStoreFiles
> >
>
> The higher this is, the bigger the price you'll pay if a server
> crashes because this will be the upper bound on how many WAL logs we
> need to split for the server before its regions come back on line
> again.  Leave it default I'd say for now.
>

Ok, we'll leave it default for now.


> > Is there some rule of thumb that I can use to determine good values for
> > these properties?
> >
>
> You've checked out this section of the book:
> http://hbase.apache.org/book.html#performance
>
> Are you filling the machines?   Are they burning cpu?  Or io-bound?
> If not, perhaps open the front gate wider by upping the number of
> concurrent handlers.
>

I have read through that section of the HBase book.  There is plenty of CPU
available.  How do I up the number of concurrent handlers?  Increase
hbase.regionserver.handler.count ?

- Amit

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