RE: compaction throughput rate not even close to 16MB
Our experience with compactions shows that more columns to merge for the same
row, more CPU it takes.
For example, testing and choosing between 2 data models with supercolumns (we
still need supercolumns since composite columns lacks some functionality):
1. supercolumns with many columns
2. supercolumns with one column (columns from model 1 merged to one blob
value)
We found that model 2 compaction performs 4 times faster.
The same for regular column families.
Best regards / Pagarbiai
Viktor Jevdokimov
Senior Developer
Email: viktor.jevdoki...@adform.com
Phone: +370 5 212 3063
Fax: +370 5 261 0453
J. Jasinskio 16C,
LT-01112 Vilnius,
Lithuania
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From: Hiller, Dean [mailto:dean.hil...@nrel.gov]
Sent: Wednesday, April 24, 2013 23:38
To: user@cassandra.apache.org
Subject: Re: compaction throughput rate not even close to 16MB
Thanks much!!! Better to hear at least one other person sees the same thing
;). Sometimes these posts just go silent.
Dean
From: Edward Capriolo
edlinuxg...@gmail.commailto:edlinuxg...@gmail.com
Reply-To:
user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Date: Wednesday, April 24, 2013 2:33 PM
To: user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Subject: Re: compaction throughput rate not even close to 16MB
I have noticed the same. I think in the real world your compaction
throughput is limited by other things. If I had to speculate I would say that
compaction can remove expired tombstones, however doing this requires
bloom filter checks, etc.
I think that setting is more important with multi threaded compaction and/or
more compaction slots. In those cases it may actually throttle something.
On Wed, Apr 24, 2013 at 3:54 PM, Hiller, Dean
dean.hil...@nrel.govmailto:dean.hil...@nrel.gov wrote:
I was wondering about the compactionthroughput. I never see ours get
even close to 16MB and I thought this is supposed to throttle compaction,
right? Ours is constantly less than 3MB/sec from looking at our logs or do I
have this totally wrong? How can I see the real throughput so that I can
understand how to throttle it when I need to?
94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms =
2.365603MB/s. 2,350,114 total rows, 2,350,022 unique. Row merge counts
were {1:2349930, 2:92, }
Thanks,
Dean
compaction throughput rate not even close to 16MB
I was wondering about the compactionthroughput. I never see ours get even
close to 16MB and I thought this is supposed to throttle compaction, right?
Ours is constantly less than 3MB/sec from looking at our logs or do I have this
totally wrong? How can I see the real throughput so that I can understand how
to throttle it when I need to?
94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms = 2.365603MB/s.
2,350,114 total rows, 2,350,022 unique. Row merge counts were {1:2349930,
2:92, }
Thanks,
Dean
Re: compaction throughput rate not even close to 16MB
I have noticed the same. I think in the real world your compaction
throughput is limited by other things. If I had to speculate I would say
that compaction can remove expired tombstones, however doing this requires
bloom filter checks, etc.
I think that setting is more important with multi threaded compaction
and/or more compaction slots. In those cases it may actually throttle
something.
On Wed, Apr 24, 2013 at 3:54 PM, Hiller, Dean dean.hil...@nrel.gov wrote:
I was wondering about the compactionthroughput. I never see ours get even
close to 16MB and I thought this is supposed to throttle compaction, right?
Ours is constantly less than 3MB/sec from looking at our logs or do I have
this totally wrong? How can I see the real throughput so that I can
understand how to throttle it when I need to?
94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms =
2.365603MB/s. 2,350,114 total rows, 2,350,022 unique. Row merge counts
were {1:2349930, 2:92, }
Thanks,
Dean
Re: compaction throughput rate not even close to 16MB
On Wed, Apr 24, 2013 at 1:33 PM, Edward Capriolo edlinuxg...@gmail.com wrote: I think that setting is more important with multi threaded compaction and/or more compaction slots. In those cases it may actually throttle something. Or if you're simultaneously doing a repair, which does a validation compaction, which will (should?) also be subject to the throttle? =Rob
Re: compaction throughput rate not even close to 16MB
Thanks much!!! Better to hear at least one other person sees the same thing
;). Sometimes these posts just go silent.
Dean
From: Edward Capriolo edlinuxg...@gmail.commailto:edlinuxg...@gmail.com
Reply-To: user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Date: Wednesday, April 24, 2013 2:33 PM
To: user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Subject: Re: compaction throughput rate not even close to 16MB
I have noticed the same. I think in the real world your compaction throughput
is limited by other things. If I had to speculate I would say that compaction
can remove expired tombstones, however doing this requires bloom filter checks,
etc.
I think that setting is more important with multi threaded compaction and/or
more compaction slots. In those cases it may actually throttle something.
On Wed, Apr 24, 2013 at 3:54 PM, Hiller, Dean
dean.hil...@nrel.govmailto:dean.hil...@nrel.gov wrote:
I was wondering about the compactionthroughput. I never see ours get even
close to 16MB and I thought this is supposed to throttle compaction, right?
Ours is constantly less than 3MB/sec from looking at our logs or do I have this
totally wrong? How can I see the real throughput so that I can understand how
to throttle it when I need to?
94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms = 2.365603MB/s.
2,350,114 total rows, 2,350,022 unique. Row merge counts were {1:2349930,
2:92, }
Thanks,
Dean
Re: compaction throughput rate not even close to 16MB
Same here. We disable the throttling and our disk and CPU usage both low (
10%) and still takes hours for LCS compaction to finish after a repair. For
this cluster, we don't delete any data, so we can rule out tombstones. Not sure
what is holding compaction back. My observation is that for the LCS which
involves large number of SSTables (since we set SSTable size too small at 10M
and sometimes one compactions involves up to 10 G of data = 1000 SSTables), the
throughout put is smaller. So my theory is that open/close file handlers have
substantial impact on the throughput.
By the way, we are on SSD.
-Wei
From: Hiller, Dean dean.hil...@nrel.gov
To: user@cassandra.apache.org user@cassandra.apache.org
Sent: Wednesday, April 24, 2013 1:37 PM
Subject: Re: compaction throughput rate not even close to 16MB
Thanks much!!! Better to hear at least one other person sees the same thing
;). Sometimes these posts just go silent.
Dean
From: Edward Capriolo edlinuxg...@gmail.commailto:edlinuxg...@gmail.com
Reply-To: user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Date: Wednesday, April 24, 2013 2:33 PM
To: user@cassandra.apache.orgmailto:user@cassandra.apache.org
user@cassandra.apache.orgmailto:user@cassandra.apache.org
Subject: Re: compaction throughput rate not even close to 16MB
I have noticed the same. I think in the real world your compaction throughput
is limited by other things. If I had to speculate I would say that compaction
can remove expired tombstones, however doing this requires bloom filter checks,
etc.
I think that setting is more important with multi threaded compaction and/or
more compaction slots. In those cases it may actually throttle something.
On Wed, Apr 24, 2013 at 3:54 PM, Hiller, Dean
dean.hil...@nrel.govmailto:dean.hil...@nrel.gov wrote:
I was wondering about the compactionthroughput. I never see ours get even
close to 16MB and I thought this is supposed to throttle compaction, right?
Ours is constantly less than 3MB/sec from looking at our logs or do I have this
totally wrong? How can I see the real throughput so that I can understand how
to throttle it when I need to?
94,940,780 bytes to 95,346,024 (~100% of original) in 38,438ms = 2.365603MB/s.
2,350,114 total rows, 2,350,022 unique. Row merge counts were {1:2349930,
2:92, }
Thanks,
Dean
