Re: Reduced write performance when reading

2015-07-29 Thread Soerian Lieve
Found the problem, it turns out that what Bharatendra suggested was correct. I had set the memtable_flush_writers to equal the number of cores but hadn't restarted the Cassandra process, so they didn't take the configuration. On Wed, Jul 29, 2015 at 12:59 PM, Robert Coli rc...@eventbrite.com

Re: Reduced write performance when reading

2015-07-29 Thread Robert Coli
On Tue, Jul 28, 2015 at 4:49 PM, Soerian Lieve sli...@liveramp.com wrote: I did already set that to the number of cores of the machines (24), but it made no difference. I continue to suggest that you file a JIRA ticket... I feel you have done sufficient community based due dilligence to

Re: Reduced write performance when reading

2015-07-28 Thread Bharatendra Boddu
Increase memtable_flush_writers. In cassandra.yaml, it was recommended to increase this setting when SSDs used for storing data. On Fri, Jul 24, 2015 at 1:55 PM, Soerian Lieve sli...@liveramp.com wrote: I was on CFQ so I changed it to noop. The problem still persisted however. Do you have any

Re: Reduced write performance when reading

2015-07-28 Thread Soerian Lieve
I did already set that to the number of cores of the machines (24), but it made no difference. On Tue, Jul 28, 2015 at 4:44 PM, Bharatendra Boddu bharatend...@gmail.com wrote: Increase memtable_flush_writers. In cassandra.yaml, it was recommended to increase this setting when SSDs used for

Re: Reduced write performance when reading

2015-07-24 Thread Soerian Lieve
I was on CFQ so I changed it to noop. The problem still persisted however. Do you have any other ideas? On Thu, Jul 23, 2015 at 5:00 PM, Jeff Ferland j...@tubularlabs.com wrote: Imbalanced disk use is ok in itself. It’s only saturated throughput that’s harmful. RAID 0 does give more consistent

Re: Reduced write performance when reading

2015-07-23 Thread Jeff Ferland
Imbalanced disk use is ok in itself. It’s only saturated throughput that’s harmful. RAID 0 does give more consistent throughput and balancing, but that’s another story. As for your situation with SSD drive, you can probably tweak this by changing the scheduler is set to noop, or read up on

Re: Reduced write performance when reading

2015-07-23 Thread Jeff Ferland
My immediate guess: your transaction logs are on the same media as your sstables and your OS prioritizes read requests. -Jeff On Jul 23, 2015, at 2:51 PM, Soerian Lieve sli...@liveramp.com wrote: Hi, I am currently performing benchmarks on Cassandra. Independently from each other I am

Reduced write performance when reading

2015-07-23 Thread Soerian Lieve
Hi, I am currently performing benchmarks on Cassandra. Independently from each other I am seeing ~100k writes/sec and ~50k reads/sec. When I read and write at the same time, writing drops down to ~1000 writes/sec and reading stays roughly the same. The heap used is the same as when only reading,

Re: Reduced write performance when reading

2015-07-23 Thread Soerian Lieve
I set up RAID0 after experiencing highly imbalanced disk usage with a JBOD setup so my transaction logs are indeed on the same media as the sstables. Is there any alternative to setting up RAID0 that doesn't have this issue? On Thu, Jul 23, 2015 at 4:03 PM, Jeff Ferland j...@tubularlabs.com