On Wed, Feb 20, 2013 at 6:47 PM, Kanwar Sangha kan...@mavenir.com wrote:
Hi – I am looking for some inputs on the file storage in Cassandra. Each
file size can range from 200kb – 3MB. I don’t see any limitation on the
column size. But would it be a good idea to store these files as binary in
Hello,
We are using Cassandra 1.2.0.
We have a cluster of 16 physical nodes, each node has 256 virtual nodes.
We want to add 2 new nodes in our cluster : we follow the procedure as
explained here :
http://www.datastax.com/docs/1.2/operations/add_replace_nodes.
After starting 1 of the new node,
Hi - What is the approximate overhead of the key cache ? Say each key is 50
bytes. What would be the overhead for this key in the key cache ?
Thanks,
Kanwar
Thanks Aaron,
I hear you on the unchartered territory bit, we're definitely not gonna
risk our live data unless we know it's safe to do what we suggested. :-) Oh
well, I guess we'll have to setup a survey node instead.
/Henrik
On Thu, Feb 21, 2013 at 4:54 AM, aaron morton
Ok.. Cassandra default block size is 256k ? Now say my data in the column is 4
MB. And the disk is giving me 4k block size random reads @ 100 IOPS. I can
read max 400k in one seek ? does that mean I would need multiple seeks to get
the complete data ?
-Original Message-
From:
Hi,
On Feb 21, 2013, at 7:52 , Kanwar Sangha kan...@mavenir.com wrote:
Hi – Can someone explain the worst case IOPS for a read ? No key cache, No
row cache, sampling rate say 512.
1) Bloom filter will be checked to see existence of key (In RAM)
2) Index filer sample (IN RAM)
I would like to understand how we can capture network latencies between a
1GbE and 10GbE for ex.
Cassandra reports two latencies.
The CF latencies reported by nodetool cfstats, nodetool cfhistograms and the CF
MBeans cover the local time it takes to read or write the data. This does not
CQL does not support offset but does have limit.
See
http://www.datastax.com/docs/1.2/cql_cli/cql/SELECT#specifying-rows-returned-using-limit
Cheers
-
Aaron Morton
Freelance Cassandra Developer
New Zealand
@aaronmorton
http://www.thelastpickle.com
On 20/02/2013, at 1:47 PM,
My first guess would be the bloom filter and index sampling from lots-o-rows
Check the row count in cfstats
Check the bloom filter size in cfstats.
Background on memory requirements
http://www.mail-archive.com/user@cassandra.apache.org/msg25762.html
Cheers
-
Aaron Morton
Hi – I have around 6TB of data on 1 node
Unless you have SSD and 10GbE you probably have too much data on there.
Remember you need to run repair and that can take a long time with a lot of
data. Also you may need to replace a node one day and moving 6TB will take a
while.
Or will the
Some things to consider:
Check for contention around the switch lock. This can happen if you get a lot
of tables flushing at the same time, or if you have a lot of secondary indexes.
It shows up as a pattern in the logs. As soon a the writer starts flushing a
memtable another will be queued.
What does rpc_timeout control? Only the reads/writes?
Yes.
like data stream,
streaming_socket_timeout_in_ms in the yaml
merkle tree request?
Either no time out or a number of days, cannot remember which right now.
What is the side effect if it's set to a really small number, say 20ms?
Cannot comment too much on the jmap but I can add my general compaction is
hurting strategy.
Try any or all of the following to get to a stable setup, then increase until
things go bang.
Set concurrent compactors to 2.
Reduce compaction throughput by half.
Reduce
Roughly how much data do you have per node?
Sent from my iPhone
On Feb 20, 2013, at 10:49 AM, Hiller, Dean dean.hil...@nrel.gov wrote:
I took this jmap dump of cassandra(in production). Before I restarted the
whole production cluster, I had some nodes running compaction and it looked
like
No.
The default size tiered strategy compacts files what are roughly the same size,
and only when there are more than 4 (default) of them.
Ok. So for 10 TB, I could have at least 4 SStables files each of 2.5 TB ?
From: aaron morton [mailto:aa...@thelastpickle.com]
Sent: 21 February 2013 11:01
If you are lazy like me wolfram alpha can help
http://www.wolframalpha.com/input/?i=transfer+42TB+at+10GbEa=UnitClash_*TB.*Tebibytes--
10 hours 15 minutes 43.59 seconds
Cheers
-
Aaron Morton
Freelance Cassandra Developer
New Zealand
@aaronmorton
http://www.thelastpickle.com
This is the key cache entry
https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cache/KeyCacheKey.java
Note that the Descriptor is re-used.
If you want to see key cache metrics, including bytes used, use nodetool info.
Cheers
-
Aaron Morton
Freelance
Thank you- indeed my index interval is 64 with a CF of 300M rows + bloom filter
false positive chance was default.
Raising the index interval to 512 didn't fix this alone, so I guess I'll have
to set the bloom filter to some reasonable value and scrub.
From: aaron morton
To avoid disk I/Os, the best option we thought is to have data in memory.
Is it a good idea to have memtable setup around 1/2 or 3/4 of
heap size? Obviously flushing will take a lot of time but would
that hurt that node's performance big time?
Start with the defaults and test your
“The limiting factors are the time it take to repair, the time it takes to
replace a node, the memory considerations for 100's of millions of rows. If you
the performance of those operations is acceptable to you, then go crazy”
If I have a node which is attached to a RAID and the node crashes
Hi - Is it a good idea to use Cassandra with SAN ? Say a SAN which provides me
8 Petabytes of storage. Would I not be I/O bound irrespective of the no of
Cassandra machines and scaling by adding
machines won't help ?
Thanks
Kanwar
No, this is a really really bad idea and C* was not designed for this, in fact,
it was designed so you don't need to have a large expensive SAN.
Don't be tempted by the shiny expensive SAN. :)
If money is no object instead throw SSD's in your nodes and run 10G between
racks
From: Kanwar
The theoretical maximum of 10G is not even close to what you actually get.
Ok. What would be the drawbacks :)
From: Michael Kjellman [mailto:mkjell...@barracuda.com]
Sent: 21 February 2013 17:12
To: user@cassandra.apache.org
Subject: Re: Cassandra with SAN
No, this is a really really bad idea and C* was not designed for this, in fact,
it was designed so you don't need
Who breaks a butterfly upon a wheel?
It will work, but you'd have a distributed database running on a single point
of failure storage fabric, thus destroying much of your benefits, unless you
have enough discrete SAN units that you treat them as racks in your cassandra
topology to ensure that
Adding a Single Point of Failure when you chose a distributed database for
probably a good reason. I'd also think you'd be tempted to have multiple
terabytes per node. (so you're even more cost inefficient because you'll still
need to buy the same number of nodes everyone else does even though
Cassandra is designed to write and read data in a way that is optimized for
physical spinning disks.
Running C* on a SAN introduces a layer of abstraction that, at best negates
those optimizations, and at worst introduces additional overhead.
Sent from my iPhone
On Feb 21, 2013, at 6:42 PM,
I shouldn't have used the word spinning... SSDs are a great option as well.
I also agree with all the expensive SPOF points others have made.
Sent from my iPhone
On Feb 21, 2013, at 6:56 PM, P. Taylor Goetz ptgo...@gmail.com wrote:
Cassandra is designed to write and read data in a way that is
There is a limit option, find it in the doc.
On Fri, Feb 22, 2013 at 3:41 AM, Sri Ramya ramya.1...@gmail.com wrote:
hi,,
Cassandra can display maximum 100 rows in a Columnfamily. can i increase
it. If it is possible please mention here.
Thank you
On Tue, Feb 19, 2013 at 1:02 PM, Anurag Gujral anurag.guj...@gmail.com wrote:
Unsubscribe me please.
Thanks
Could I interest you in picture of a lemur instead?
http://goo.gl/RZw3e
--
Eric Evans
Acunu | http://www.acunu.com | @acunu
As a counter argument though, anyone running a C* cluster on the Amazon
cloud is going to be using SAN storage (or some kind of proprietary storage
array) at the lowest layers...Amazon isn't going to have a bunch of JBOD
running their cloud infrastructure. However, they've invested in the
On Friday, February 22, 2013, Jared Biel wrote:
As a counter argument though, anyone running a C* cluster on the Amazon
cloud is going to be using SAN storage (or some kind of proprietary storage
array) at the lowest layers...Amazon isn't going to have a bunch of JBOD
running their cloud
Bill de hÓra already answered, I'd like to add:
To achieve ~4ms reads (from client standpoint):
1. You can't use multi-slice, since different keys may occur on different nodes
that require internode communication. Design you data and reads to use one
key/row.
2. Use ConsistencyLevel.ONE to
Thanks Aaron for the great information as always. I just checked cfhistograms
and only a handful of read latency are bigger than 100ms, but for
proxyhistograms there are 10 times more are greater than 100ms. We are using
QUORUM for reading with RF=3, and I understand coordinator needs to get
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