Re: IO scheduler for SSDs on EC2?

Hi Ali, The best practice is to use the noop scheduler on array of SSDs behind your block device (Hardware RAID controller). If you are using only one SSD disk, the deadline scheduler is the best choice to reduce IO latency. It is not recommended to set cfq on SSDs disks. Regards, Roni

Downgrade Cassandra from 2.1.x to 2.0.x

Hi there, What is the best way to downgrade a C* 2.1.3 cluster to the stable 2.0.12? I know it's not supported, but we are getting too many issues with the 2.1.x... It is leading us to think that the best solution is to use the stable version. Is there a safe way to do that? Cheers, Roni

OOM and high SSTables count

Hi there, We are running C* 2.1.3 cluster with 2 DataCenters: DC1: 30 Servers / DC2 - 10 Servers. DC1 servers have 32GB of RAM and 10GB of HEAP. DC2 machines have 16GB of RAM and 5GB HEAP. DC1 nodes have about 1.4TB of data and DC2 nodes 2.3TB. DC2 is used only for backup purposes. There are no re

Re: Possible problem with disk latency

r your nodes to be sure that the value is not too high. You may get too much IO if you increase concurrent compactors when using spinning disks. Regards, Roni Balthazar On 25 February 2015 at 16:37, Ja Sam wrote: > Hi, > One more thing. Hinted Handoff for last week for all nodes was less t

Re: Possible problem with disk latency

Hi Piotr, Are your repairs finishing without errors? Regards, Roni Balthazar On 25 February 2015 at 15:43, Ja Sam wrote: > Hi, Roni, > They aren't exactly balanced but as I wrote before they are in range from > 2500-6000. > If you need exactly data I will check them tomorrow

Re: Possible problem with disk latency

> Piotrek. > > p.s. I don't know why my mail client display my name as Ja Sam instead of > Piotr Stapp, but this doesn't change anything :) > > > On Wed, Feb 25, 2015 at 5:45 PM, Roni Balthazar > wrote: >> >> Hi Ja, >> >> How are the pendi

Re: Possible problem with disk latency

ool cfstats" on your nodes. Cheers, Roni Balthazar On 25 February 2015 at 13:29, Ja Sam wrote: > I do NOT have SSD. I have normal HDD group by JBOD. > My CF have SizeTieredCompactionStrategy > I am using local quorum for reads and writes. To be precise I have a lot of > writes

Re: Many pending compactions

Try repair -pr on all nodes. If after that you still have issues, you can try to rebuild the SSTables using nodetool upgradesstables or scrub. Regards, Roni Balthazar > Em 18/02/2015, às 14:13, Ja Sam escreveu: > > ad 3) I did this already yesterday (setcompactionthrouput also).

Re: Many pending compactions

you getting when running repairs. Regards, Roni Balthazar On Wed, Feb 18, 2015 at 1:31 PM, Ja Sam wrote: > Can you explain me what is the correlation between growing SSTables and > repair? > I was sure, until your mail, that repair is only to make data consistent > between nodes.

Re: Many pending compactions

pactions must decrease as well... Cheers, Roni Balthazar On Wed, Feb 18, 2015 at 12:39 PM, Ja Sam wrote: > 1) we tried to run repairs but they usually does not succeed. But we had > Leveled compaction before. Last week we ALTER tables to STCS, because guys > from DataStax suggest us

Re: Many pending compactions

/dml_config_consistency_c.html Cheers, Roni Balthazar On Wed, Feb 18, 2015 at 11:07 AM, Ja Sam wrote: > I don't have problems with DC_B (replica) only in DC_A(my system write only > to it) I have read timeouts. > > I checked in OpsCenter SSTable count and I have: > 1) in DC_A same +-

Re: Many pending compactions

(eg: driver's timeout, concurrent reads and so on) Regards, Roni Balthazar On Wed, Feb 18, 2015 at 9:51 AM, Ja Sam wrote: > Hi, > Thanks for your "tip" it looks that something changed - I still don't know > if it is ok. > > My nodes started to do more compac

Re: Many pending compactions

HI, Yes... I had the same issue and setting cold_reads_to_omit to 0.0 was the solution... The number of SSTables decreased from many thousands to a number below a hundred and the SSTables are now much bigger with several gigabytes (most of them). Cheers, Roni Balthazar On Tue, Feb 17, 2015

Re: Many pending compactions

ht or when your IO is not busy. >From http://wiki.apache.org/cassandra/NodeTool: 0 0 * * * root nodetool -h `hostname` setcompactionthroughput 999 0 6 * * * root nodetool -h `hostname` setcompactionthroughput 16 Cheers, Roni Balthazar On Mon, Feb 16, 2015 at 7:47 PM, Ja Sam wrote: > On

Re: High read latency after data volume increased

://pastebin.com/jbAgDzVK Thanks, Roni Balthazar On Fri, Jan 9, 2015 at 12:03 PM, datastax wrote: > Hello > > You may not be experiencing versioning issues. Do you know if compaction > is keeping up with your workload? The behavior described in the subject is > typically

Re: High read latency after data volume increased

me know if I need to provide more information. Thanks, Roni Balthazar On Thu, Jan 8, 2015 at 5:23 PM, Robert Coli wrote: > On Thu, Jan 8, 2015 at 11:14 AM, Roni Balthazar > wrote: > >> We are using C* 2.1.2 with 2 DCs. 30 nodes DC1 and 10 nodes DC2. >> > > https:/

High read latency after data volume increased

moryError: Java heap space" Any hints? Regards, Roni Balthazar

Re: Operating on large cluster

Hi, We use Puppet to manage our Cassandra configuration. (http://puppetlabs.com) You can use Cluster SSH to send commands to the server as well. Another good choice is Saltstack. Regards, Roni On Thu, Oct 23, 2014 at 5:18 AM, Alain RODRIGUEZ wrote: > Hi, > > I was wondering about how do you