Regarding Consistent Hashing....
ajinkya at truesparrow.com
Thu Aug 30 11:02:39 UTC 2007
Our application servers are local to EC2.
Now, my next question is which library will be better for Consistent Hashing
in terms of both performance and stability -
a) pecl/memcached client (from CVS)
What is the difference between the two implementations?
Also, where will we find latest version of libketama?
Please let me know.
Thanks in advance.
From: dormando [mailto:dormando at rydia.net]
Sent: Thursday, August 30, 2007 2:14 PM
To: Ajinkya Nahar
Cc: memcached at lists.danga.com; sunil at truesparrow.com; 'Nishith Shah'
Subject: Re: Regarding Consistent Hashing....
Ajinkya Nahar wrote:
> Basically, we are using Amazon's EC2 servers as memcached servers.
> So as and when we see an increase in traffic/load, we expect to add more
> EC2 servers to the memcached cloud. And when the traffic/load subsides
> (lets say after a week or so), we might remove a few servers from the
> In such a scenario, if using normal hashing, I believe we would have to
> flush everything when adding/removing memcached servers.
> Do you think doing this might cause the system to go in a spin and might
> be a risky proposition, and so we should rather consider using
> consistent hashing?
> Or do you think this is not a big deal and we should rather use the
> regular hashing (which is more stable)?
> Please let me know your comments on this.
Are your application servers local to EC2 as well? If not, I can't
imagine the latency being any good for the system, and it'd have to be
over fat CPU intensive encrypted links. Memcached's not very CPU heavy,
so I don't really see it being that great of a use for EC2. It thrives
on fast local links with massive gobs of RAM.
Just use consistent hashing if you're worried. There should be enough
libraries to work, or you can test the pecl client, or use libketama if
you use php. Hard to go wrong with it.
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