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From hajjat <haj...@purdue.edu>
Subject Recommended data size for Reads/Writes in Cassandra
Date Thu, 18 Jul 2013 21:03:19 GMT
Hi,

Is there a recommended data size for Reads/Writes in Cassandra? I tried
inserting 10 MB objects and the latency I got was pretty high. Also, I was
never able to insert larger objects (say 50 MB) since Cassandra kept
crashing when I tried that.

Here is my experiment setup: 
I used two Large VMs in EC2 within the same data-center. Inserts have ALL
consistency (strong consistency).  The latencies were as follows:
Data size:	10 MB		1 MB		100 Bytes
Latency:	250ms		50ms		8ms

I've also done the same for two Large VMs across two data-centers. The
latencies were around:
Data size:	10 MB		1 MB		100 Bytes
Latency:	1200ms		800ms	80ms

1) Ain't the 10 MB latency extremely high? 
2) Is there a recommended data size to use with Cassandra (e.g., a few bytes
up to 1 MB)?
3) Also, I tried inserting 50 MB data but Cassandra kept crashing. Does
anybody know why? I thought the max data size should be up to 2 GB?

Thanks,
Mohammad

PS. Here is my python code I use to insert into Cassandra. I put my
stopwatch timers around the insert statement:
    fh = open(TEST_FILE,'r')
    data = str(fh.read())

    POOL = ConnectionPool(keyspace, server_list=['localhost:9160'],
timeout=None)
    USER = ColumnFamily(POOL, 'User')
    USER.insert('Ali', {'data':
data},write_consistency_level=pycassa.cassandra.ttypes.ConsistencyLevel.ALL)




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