High latency, low performance, Azure

#1

Hi,

I have 2 couchbase servers running on 2 A1 virtual machines on Azure with 1 replica.
An Azure website is connected to them using .Net SDK.
Everything work.

The 3 endpoints are within a virtual network and resides near each other.
All the servers are idle, data size is small. Server’s CPU usage according to console is 5%. Ram usage is 33%.

Latency of only one get command of one document is at least 250ms, not sub-millisecond as expected.
For local dev, latency is usually 83ms using the same cluster
What am I doing wrong ?

Itay

#2

Found it !

log4net introduced a delay while on remote.
Anyone knows how to enable log4net only on local host ?

Now latency is at most ~15ms.
What should be my next step to reduce it to sub-millisecond ?

#3

Hi itay,
To get the best possible performance, the Azure VM’s needs to be at least 4 core (recommended minimum). This number of cores allows CB Server to run it’s core processes on separate cores.

The next topic with high impact is network latency, therefore it’s most optimal to host the application server within the same VN as the CB nodes. The application server is then responsible for “talking” to the external clients (with respect to Azure)

I hope this helps.

You can read my blog series to get a bit more insight and a test program written in .NET
http://blog.couchbase.com/hosting-couchbase-server-in-windows-azure-part-1

Thanks
Martin

#4

Thanks,

You wrote an important post that helps a lot.

Do you also experience 15ms latency with 2 A1 on the same VN ?
BTW, if I upgrade to A2 the latency drops to <1ms so the network latency is very small on its own, so my question is: Is the latency only the result of processing power, even though the data should be in cache, as I mostly re-read same docs ?

Itay

#5

My experience is that latency is highly bound to number of cores, more cores lower latency. But only to a certain level then network latency (Endpoint, Cloud FirewallI) seems to be the primary reason for latency.

Hope this helps