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From Theo Hultberg <t...@iconara.net>
Subject Re: does anyone store large values in cassandra e.g. 100kb?
Date Tue, 09 Jul 2013 17:30:20 GMT
yes, by splitting the rows into 36 parts it's very rare that any part gets
big enough to impact the clusters performance. there are still rows that
are bigger than the in memory compaction limit, but when it's only some it
doesn't matter as much.

T#


On Tue, Jul 9, 2013 at 5:43 PM, S Ahmed <sahmed1020@gmail.com> wrote:

> So was the point of breaking into 36 parts to bring each row to the 64 or
> 128mb threshold?
>
>
> On Tue, Jul 9, 2013 at 3:18 AM, Theo Hultberg <theo@iconara.net> wrote:
>
>> We store objects that are a couple of tens of K, sometimes 100K, and we
>> store quite a few of these per row, sometimes hundreds of thousands.
>>
>> One problem we encountered early was that these rows would become so big
>> that C* couldn't compact the rows in-memory and had to revert to slow
>> two-pass compactions where it spills partially compacted rows to disk. we
>> solved that in two ways, first by
>> increasing in_memory_compaction_limit_in_mb from 64 to 128, and although it
>> helped a little bit we quickly realized didn't have much effect because
>> most of the time was taken up by really huge rows many times larger than
>> that.
>>
>> We ended up implementing a simple sharding scheme where each row is
>> actually 36 rows that each contain 1/36 of the range (we take the first
>> letter in the column key and stick that on the row key on writes, and on
>> reads we read all 36 rows -- 36 because there are 36 letters and numbers in
>> the ascii alphabet and our column keys happen to distribute over that quite
>> nicely).
>>
>> Cassandra works well with semi-large objects, and it works well with wide
>> rows, but you have to be careful about the combination where rows get
>> larger than 64 Mb.
>>
>> T#
>>
>>
>> On Mon, Jul 8, 2013 at 8:13 PM, S Ahmed <sahmed1020@gmail.com> wrote:
>>
>>> Hi Peter,
>>>
>>> Can you describe your environment, # of documents and what kind of usage
>>> pattern you have?
>>>
>>>
>>>
>>>
>>> On Mon, Jul 8, 2013 at 2:06 PM, Peter Lin <woolfel@gmail.com> wrote:
>>>
>>>> I regularly store word and pdf docs in cassandra without any issues.
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Jul 8, 2013 at 1:46 PM, S Ahmed <sahmed1020@gmail.com> wrote:
>>>>
>>>>> I'm guessing that most people use cassandra to store relatively
>>>>> smaller payloads like 1-5kb in size.
>>>>>
>>>>> Is there anyone using it to store say 100kb (1/10 of a megabyte) and
>>>>> if so, was there any tweaking or gotchas that you ran into?
>>>>>
>>>>
>>>>
>>>
>>
>

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