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From Theo Hultberg <>
Subject Re: does anyone store large values in cassandra e.g. 100kb?
Date Tue, 09 Jul 2013 07:18:16 GMT
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

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

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.


On Mon, Jul 8, 2013 at 8:13 PM, S Ahmed <> 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 <> wrote:
>> I regularly store word and pdf docs in cassandra without any issues.
>> On Mon, Jul 8, 2013 at 1:46 PM, S Ahmed <> 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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