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From James Golick <jamesgol...@gmail.com>
Subject Re: Read Performance
Date Thu, 01 Apr 2010 20:36:48 GMT
I don't have the additional hardware to try to isolate this issue atm, so I
decided to push some code that performs 20% of reads directly from
cassandra. The cache hit rate has gone up to about 88% now and it's still
climbing, albeit slowly. There remains plenty of free cache space.

So far, the average time to multi_get those 20 rows is still hovering around
35-45ms.

I'll report back with more info as it comes in.

On Thu, Apr 1, 2010 at 12:06 AM, Cemal Dalar <cemal.dalar@gmail.com> wrote:

> Hi James,
>
> I don't know how to get the below statistics data and calculate the access
> times (read/write in ms) in your previous mails. Can you explain a little?
> Iike to work on it also.
>
> CD
>
>
> On Thu, Apr 1, 2010 at 4:15 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>
>> On Wed, Mar 31, 2010 at 6:21 PM, James Golick <jamesgolick@gmail.com>
>> wrote:
>> > Keyspace: ActivityFeed
>> >         Read Count: 699443
>> >         Read Latency: 16.11017477192566 ms.
>>
>> >                 Column Family: Events
>> >                 Read Count: 232378
>> >                 Read Latency: 0.396 ms.
>> >                 Row cache capacity: 500000
>> >                 Row cache size: 62768
>> >                 Row cache hit rate: 0.007716049382716049
>>
>> This says that
>>
>>  - recent queries to Events are much faster than the lifetime average
>> for your Keyspace
>>  - even though you have almost no row cache hits (~1700 out of 232000
>> reads)
>>
>> Not sure what to make of that, tbh.  If it were me I would try to
>> reproduce on a test machine w/o all that pesky live traffic confusing
>> things.
>>
>> -Jonathan
>>
>
>

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