slow 2 node cluster

Aphyr aphyr at
Sun Nov 20 16:59:37 EST 2011

On 11/20/2011 01:34 PM, Catalin Constantin wrote:
> To make it simple. No more networking. Just one node (with n = 1) and
> local tests.
> The producing of data is a simple CSV file read (ruled out too cause
> this is fast).

Read from the same disk? If you're interleaving every write with a read 
from this file, how many back-forth seeks do you think your disk is doing?

> HDD: 2 x 750 GB SATA 2 (RAID1)

Hint hint hint.

> What insert rate should i expect on a normal Debian 6.0 64 bit
> installation (no tweaks) ?

450 inserts/second. Or, if you address some of the points I mentioned 
earlier, perhaps 2000-4000/sec, depending on write characteristics. Most 
people find performance improves linearly with nodes, so long as the 
network is not the bottleneck.

Our six-node cluster (bitcask-dedicated SSDs, 2x bonded gige, 2:1 
read:write ratio, median value ~10 kB, n_val 3, typical r/w: quorum) 
tops out at about 3,000 aggregate ops/sec while maintaining reasonable 
(~10ms 99%) latencies. I can push it higher if I relax latency constraints.

> I can only compare it with other DBs i have tested on the same machine:
> ex: mongodb, kyototycoon

These databases solve different problems in different ways. You should 
expect them to perform differently. The question is: for your workload, 
what balance of raw IOPS, redundancy, availability, latency, and 
conflict handling model fits best? Riak trades IOPS for availability and 
redundancy, and trades MVCC/locking for vclock resolution.


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