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From Jonathan Ellis <>
Subject Re: cassandra freezes
Date Thu, 25 Feb 2010 14:56:25 GMT
Are you swapping?

otherwise there's something wrong w/ your vm (?), disk i/o doesn't
block incoming writes in cassandra

On Thu, Feb 25, 2010 at 8:49 AM, Boris Shulman <> wrote:
> I don't think it is gc related issue. There is no correlation between
> gc times and the freeze times. More over I don't see any gc activity
> that lasts for omre than o.03 sec. But there is a correlation between
> disk flushing operations. I've noticed that the system freezes each
> time when my commit log reaches 1.1G. I have 1024M memtable size so I
> assume this is when the data flushing occurs.
> On Thu, Feb 25, 2010 at 4:13 PM, Jonathan Ellis <> wrote:
>> Then you should check GC timing with -Xverbose:gc option (see:
>> for how to modify
>> jvm options) for a correlation.
>> On Thu, Feb 25, 2010 at 8:09 AM, Boris Shulman <> wrote:
>>> In these tests I perform only write operations, no reads.
>>> On Thu, Feb 25, 2010 at 4:07 PM, Jonathan Ellis <> wrote:
>>>> The only kind of "freeze" that makes sense there is your reads are i/o
>>>> bound and the extra disk activity is killing you.  In that case the
>>>> fix is to add more RAM, or give less to the JVM so the OS can use more
>>>> for buffer cache.
>>>> On Thu, Feb 25, 2010 at 8:01 AM, Boris Shulman <>
>>>>> In my case the cassandra node freezes while memtable flush operation
>>>>> is performed or compactation operation is performed. How can I
>>>>> optimize the cassandra configuration in order to avoid this behavior?
>>>>> I've tried both using large memtable size (1G) and small (128M) but in
>>>>> every case I have some sort of freezes when the data is flushed to the
>>>>> disk.
>>>>> Please advice.

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