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From Илья Шипицин <chipits...@gmail.com>
Subject Re: performance is drastically degraded after 0.7.8 --> 1.0.11 upgrade
Date Thu, 30 Aug 2012 13:44:54 GMT
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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