54 memtable flushes in hour at peaktime

[Tomer B <to...@gmail.com>]

Hi

at highest traffic hours i get 54 memtable flushes, this happens for a few
hours during the day and at the rest of hours its ranging from 0 to 10 .

Should I be doing anything about it? is that number on critical level? can i
live with 54 memtable flushes per hour during peak hours? (I might expect
higher peaks coming during this year).

(The rest of my memtables with lower traffic range at about 1-4 memtable
flushes per hour).

thanks

Re: 54 memtable flushes in hour at peaktime

[aaron morton <aa...@thelastpickle.com>]

It's not a problem by it's self, compaction will do it's thing. It you are also seeing read latency increase it may be something you want to look it.  

What version are you using ? The tuning is different (i.e. it gets easier) between versions 0.7, 0.8 and 1.0. 

It's probably just the case that you are writing a lot of data. Look for log messages from ColumnFamilyStore that start with "Enqueuing flush of Memtable…" They will tell you how many serialized bytes and operations the memtable soaked up before been flushed. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 10/10/2011, at 6:56 AM, Tomer B wrote:

> Hi
> 
> at highest traffic hours i get 54 memtable flushes, this happens for a few hours during the day and at the rest of hours its ranging from 0 to 10 .
> 
> Should I be doing anything about it? is that number on critical level? can i live with 54 memtable flushes per hour during peak hours? (I might expect higher peaks coming during this year).
> 
> (The rest of my memtables with lower traffic range at about 1-4 memtable flushes per hour).
> 
> thanks