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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: performance is drastically degraded after 0.7.8 --> 1.0.11 upgrade
Date Thu, 30 Aug 2012 15:30:44 GMT
If you move from 7.X to 0.8X or 1.0X you have to rebuild sstables as
soon as possible. If you have large bloomfilters you can hit a bug
where the bloom filters will not work properly.


On Thu, Aug 30, 2012 at 9:44 AM, Илья Шипицин <chipitsine@gmail.com> wrote:
> we are running somewhat queue-like with aggressive write-read patterns.
> I was looking for scripting queries from live Cassandra installation, but I
> didn't find any.
>
> is there something like thrift-proxy or other query logging/scripting engine
> ?
>
> 2012/8/30 aaron morton <aaron@thelastpickle.com>
>>
>> in terms of our high-rate write load cassandra1.0.11 is about 3 (three!!)
>> times slower than cassandra-0.7.8
>>
>> We've not had any reports of a performance drop off. All tests so far have
>> show improvements in both read and write performance.
>>
>> I agree, such digests save some network IO, but they seem to be very bad
>> in terms of CPU and disk IO.
>>
>> The sha1 is created so we can diagnose corruptions in the -Data component
>> of the SSTables. They are not used to save network IO.
>> It is calculated while streaming the Memtable to disk so has no impact on
>> disk IO. While not the fasted algorithm I would assume it's CPU overhead in
>> this case is minimal.
>>
>>  there's already relatively small Bloom filter file, which can be used for
>> saving network traffic instead of sha1 digest.
>>
>> Bloom filters are used to test if a row key may exist in an SSTable.
>>
>> any explanation ?
>>
>> If you can provide some more information on your use case we may be able
>> to help.
>>
>> Cheers
>>
>>
>> -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 30/08/2012, at 5:18 AM, Илья Шипицин <chipitsine@gmail.com> wrote:
>>
>> in terms of our high-rate write load cassandra1.0.11 is about 3 (three!!)
>> times slower than cassandra-0.7.8
>> after some investigation carried out I noticed files with "sha1" extension
>> (which are missing for Cassandra-0.7.8)
>>
>> in maybeWriteDigest() function I see no option fot switching sha1 digests
>> off.
>>
>> I agree, such digests save some network IO, but they seem to be very bad
>> in terms of CPU and disk IO.
>> why to use one more digest (which have to be calculated), there's already
>> relatively small Bloom filter file, which can be used for saving network
>> traffic instead of sha1 digest.
>>
>> any explanation ?
>>
>> Ilya Shipitsin
>>
>>
>

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