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From "B. Todd Burruss" <bburr...@real.com>
Subject Re: Persistently increasing read latency
Date Fri, 04 Dec 2009 00:20:49 GMT
another note on this, i stopped my client and after about 35 minutes the
compaction did complete, no more pending in compaction-pool.  however
the Index, Data, and Filter files still exist with lots of data in them.
"Compact" files exist for all but 4 of the Data files - these "compact"
files are zero length.

thx!


On Thu, 2009-12-03 at 15:40 -0800, B. Todd Burruss wrote:
> in my situation it seems like the compaction process is being starved.
> i'm hitting the server hard for the last 45 minutes and the compaction
> pool is sitting at 1 active, 25 pending, and 7 completed.  it has been
> at 1 active and 7 completed for about 20 minutes.  the pending have been
> growing steadily since then.  and as i was typing it finally finished
> another compaction, so they must be just taking forever.
> 
> snapshots of nodeprobe and iostats follow:
> 
> Pool Name                    Active   Pending      Completed
> FILEUTILS-DELETE-POOL             0         0            116
> MESSAGING-SERVICE-POOL            0         0              0
> STREAM-STAGE                      0         0              0
> RESPONSE-STAGE                    0         0              0
> ROW-READ-STAGE                    1         4        8652560
> LB-OPERATIONS                     0         0              0
> COMMITLOG                         1         0       14695623
> MESSAGE-DESERIALIZER-POOL         0         0              0
> GMFD                              0         0              0
> LB-TARGET                         0         0              0
> CONSISTENCY-MANAGER               0         0              0
> ROW-MUTATION-STAGE                1         1       14692604
> MESSAGE-STREAMING-POOL            0         0              0
> LOAD-BALANCER-STAGE               0         0              0
> FLUSH-SORTER-POOL                 0         0             28
> MEMTABLE-POST-FLUSHER             0         0             28
> COMPACTION-POOL                   1        25              7
> FLUSH-WRITER-POOL                 0         0             28
> HINTED-HANDOFF-POOL               0         0              0
> 
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           61.85    0.00   26.68    7.73    0.00    3.74
> 
> Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
> sda             246.00     11456.00     18528.00      11456      18528
> sda2          23074.00        20.50      1854.00         20       1854
> sda1              0.00         0.00         0.00          0          0
> 
> 
> 
> 
> On Thu, 2009-12-03 at 17:05 -0600, Jonathan Ellis wrote:
> > Thanks for looking into this.  Doesn't seem like there's much
> > low-hanging fruit to make compaction faster but I'll keep that in the
> > back of my mind.
> > 
> > -Jonathan
> > 
> > On Thu, Dec 3, 2009 at 4:58 PM, Freeman, Tim <tim.freeman@hp.com> wrote:
> > >>So this is working as designed, but the design is poor because it
> > >>causes confusion.  If you can open a ticket for this that would be
> > >>great.
> > >
> > > Done, see:
> > >
> > >   https://issues.apache.org/jira/browse/CASSANDRA-599
> > >
> > >>What does iostat -x 10 (for instance) say about the disk activity?
> > >
> > > rkB/s is consistently high, and wkB/s varies.  This is a typical entry with
wkB/s at the high end of its range:
> > >
> > >>avg-cpu:  %user   %nice    %sys %iowait   %idle
> > >>           1.52    0.00    1.70   27.49   69.28
> > >>
> > >>Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s avgrq-sz
avgqu-sz   await  svctm  %util
> > >>sda          3.10 3249.25 124.08 29.67 26299.30 26288.11 13149.65 13144.06
  342.04    17.75   92.25   5.98  91.92
> > >>sda1         0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00
> > >>sda2         3.10 3249.25 124.08 29.67 26299.30 26288.11 13149.65 13144.06
  342.04    17.75   92.25   5.98  91.92
> > >>sda3         0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00
> > >
> > > and at the low end:
> > >
> > >>avg-cpu:  %user   %nice    %sys %iowait   %idle
> > >>           1.50    0.00    1.77   25.80   70.93
> > >>
> > >>Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s avgrq-sz
avgqu-sz   await  svctm  %util
> > >>sda          3.40 817.10 128.60 17.70 27828.80 6600.00 13914.40  3300.00
  235.33     6.13   56.63   6.21  90.81
> > >>sda1         0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00
> > >>sda2         3.40 817.10 128.60 17.70 27828.80 6600.00 13914.40  3300.00
  235.33     6.13   56.63   6.21  90.81
> > >>sda3         0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00
> > >
> > > Tim Freeman
> > > Email: tim.freeman@hp.com
> > > Desk in Palo Alto: (650) 857-2581
> > > Home: (408) 774-1298
> > > Cell: (408) 348-7536 (No reception business hours Monday, Tuesday, and Thursday;
call my desk instead.)
> > >
> > >
> > > -----Original Message-----
> > > From: Jonathan Ellis [mailto:jbellis@gmail.com]
> > > Sent: Thursday, December 03, 2009 2:45 PM
> > > To: cassandra-user@incubator.apache.org
> > > Subject: Re: Persistently increasing read latency
> > >
> > > On Thu, Dec 3, 2009 at 4:34 PM, Freeman, Tim <tim.freeman@hp.com> wrote:
> > >>>Can you tell if the system is i/o or cpu bound during compaction?
> > >>
> > >> It's I/O bound.  It's using ~9% of 1 of 4 cores as I watch it, and all
it's doing right now is compactions.
> > >
> > > What does iostat -x 10 (for instance) say about the disk activity?
> > >
> 
> 



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