Open Stack

Hi Shrinand,

The concurrency bottleneck of Swift cluster could be various.
Here's a list :

   - Settings of each workers, workers count, max_clients,
   threads_per_disk.
   - Proxy CPU bound
   - Storage nodes CPU bound
   - Total Disk IO capacity (includes available memory for xfs caching)
   - The power of your client machines
   - Network issue


You need to analyze the monitoring data to find the real bottleneck.
The range of concurrency connections performance depends on the deployment.
Concurrent connections from 150(VMs) to 6K+(physical sever pool). Of course
that you can setup multiple proxy servers for handling higher concurrency
as long as your storage nodes can stand for it.

The path of a request in my knowing:

Client --> Proxy-server --> object-server --> container-server (optional
async) --> object-server --> Proxy-server --> Client --> close connection.


Hope it help
Hugo









2014/1/11 Shrinand Javadekar <shrinand at maginatics.com>

> Hi,
>
> This question is specific to Openstack Swift. I am trying to understand
> just how much is the proxy server a bottleneck when multiple clients are
> concurrently trying to write to a swift cluster. Has anyone done
> experiments to measure this? It'll be great to see some results.
>
> I see that the proxy-server already has a "workers" config option.
> However, looks like that is the # of threads in one proxy-server process.
> Does having multiple proxy-servers themselves, running on different nodes
> (and having some load-balancer in front of them) help in satisfying more
> concurrent writes? Or will these multiple proxy-servers also get
> bottlenecked on the account/container/obj server?
>
> Also, looking at the code in swift/proxy-server/controllers/obj.py, it
> seems that each request that the proxy-server sends to the backend servers
> (account/container/obj) is synchronous. It does not send the request and go
> back do accept more requests. Is this one of the reasons why write requests
> can be slow?
>
> Thanks in advance.
> -Shri
>
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