It's possible that there is a bad or slower disk on Gurjeet's machine. I think details of iostat and cpu would clear things up.
On Tue, Aug 21, 2012 at 4:33 PM, lars hofhansl <[email protected]> wrote: > I get roughly the same (~1.8s) - 100 rows, 200.000 columns, segment size > 100 > > > > ________________________________ > From: Gurjeet Singh <[email protected]> > To: [email protected]; lars hofhansl <[email protected]> > Sent: Tuesday, August 21, 2012 11:31 AM > Subject: Re: Slow full-table scans > > How does that compare with the newScanTable on your build ? > > Gurjeet > > On Tue, Aug 21, 2012 at 11:18 AM, lars hofhansl <[email protected]> > wrote: > > Hmm... So I tried in HBase (current trunk). > > I created 100 rows with 200.000 columns each (using your oldMakeTable). > The creation took a bit, but scanning finished in 1.8s. (HBase in pseudo > distributed mode - with your oldScanTable). > > > > -- Lars > > > > > > > > ----- Original Message ----- > > From: lars hofhansl <[email protected]> > > To: "[email protected]" <[email protected]> > > Cc: > > Sent: Monday, August 20, 2012 7:50 PM > > Subject: Re: Slow full-table scans > > > > Thanks Gurjeet, > > > > I'll (hopefully) have a look tomorrow. > > > > -- Lars > > > > > > > > ----- Original Message ----- > > From: Gurjeet Singh <[email protected]> > > To: [email protected]; lars hofhansl <[email protected]> > > Cc: > > Sent: Monday, August 20, 2012 7:42 PM > > Subject: Re: Slow full-table scans > > > > Hi Lars, > > > > Here is a testcase: > > > > https://gist.github.com/3410948 > > > > Benchmarking code: > > > > https://gist.github.com/3410952 > > > > Try running it with numRows = 100, numCols = 200000, segmentSize = 1000 > > > > Gurjeet > > > > > > On Thu, Aug 16, 2012 at 11:40 AM, Gurjeet Singh <[email protected]> > wrote: > >> Sure - I can create a minimal testcase and send it along. > >> > >> Gurjeet > >> > >> On Thu, Aug 16, 2012 at 11:36 AM, lars hofhansl <[email protected]> > wrote: > >>> That's interesting. > >>> Could you share your old and new schema. I would like to track down > the performance problems you saw. > >>> (If you had a demo program that populates your rows with 200.000 > columns in a way where you saw the performance issues, that'd be even > better, but not necessary). > >>> > >>> > >>> -- Lars > >>> > >>> > >>> > >>> ________________________________ > >>> From: Gurjeet Singh <[email protected]> > >>> To: [email protected]; lars hofhansl <[email protected]> > >>> Sent: Thursday, August 16, 2012 11:26 AM > >>> Subject: Re: Slow full-table scans > >>> > >>> Sorry for the delay guys. > >>> > >>> Here are a few results: > >>> > >>> 1. Regions in the table = 11 > >>> 2. The region servers don't appear to be very busy with the query ~5% > >>> CPU (but with parallelization, they are all busy) > >>> > >>> Finally, I changed the format of my data, such that each cell in HBase > >>> contains a chunk of a row instead of the single value it had. So, > >>> stuffing each Hbase cell with 500 columns of a row, gave me a > >>> performance boost of 1000x. It seems that the underlying issue was IO > >>> overhead per byte of actual data stored. > >>> > >>> > >>> On Wed, Aug 15, 2012 at 5:16 PM, lars hofhansl <[email protected]> > wrote: > >>>> Yeah... It looks OK. > >>>> Maybe 2G of heap is a bit low when dealing with 200.000 column rows. > >>>> > >>>> > >>>> If you can I'd like to know how busy your regionservers are during > these operations. That would be an indication on whether the > parallelization is good or not. > >>>> > >>>> -- Lars > >>>> > >>>> > >>>> ----- Original Message ----- > >>>> From: Stack <[email protected]> > >>>> To: [email protected] > >>>> Cc: > >>>> Sent: Wednesday, August 15, 2012 3:13 PM > >>>> Subject: Re: Slow full-table scans > >>>> > >>>> On Mon, Aug 13, 2012 at 6:10 PM, Gurjeet Singh <[email protected]> > wrote: > >>>>> I am beginning to think that this is a configuration issue on my > >>>>> cluster. Do the following configuration files seem sane ? > >>>>> > >>>>> hbase-env.sh https://gist.github.com/3345338 > >>>>> > >>>> > >>>> Nothing wrong w/ this (Remove the -ea, you don't want asserts in > >>>> production, and the -XX:+CMSIncrementalMode flag if >= 2 cores). > >>>> > >>>> > >>>>> hbase-site.xml https://gist.github.com/3345356 > >>>>> > >>>> > >>>> This is all defaults effectively. I don't see any of the configs. > >>>> recommended by the performance section of the reference guide and/or > >>>> those suggested by the GBIF blog. > >>>> > >>>> You don't answer LarsH's query about where you see the 4% difference. > >>>> > >>>> How many regions in your table? Whats the HBase Master UI look like > >>>> when this scan is running? > >>>> St.Ack > >>>> >
