I host my Magento store on a VPS. The Joomla website I have on it performs normal, but the Magento store is very slow and sluggish. what can I do?
Unlike Joomla websites or any other website using any other framework, Magento stores cannot function properly on VPS. Magento stores, even if they have 1 visitor per day, will always perform slow on VPS. They need far greater resources than any VPS can offer (and if you take a VPS with enough added resources like a dedicated server has, it would cost you the same to take a dedicated server). The bottom line is that for Magento store you need a dedicated server if you want your customers to stay on your store. Customers today have zero tolerance for waiting more than few milliseconds for a page to load. So while it's okay with you to wait, they won't wait and they are very much likely to go elsewhere.
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I disagree that you will need a dedicated server just for Magento store to perform well.
What is the specification of your VPS? Is it managed or unmanaged? Is it properly tuned and optimized?
It is very important that you have a good VPS or server with decent specifications and are properly tuned and optimized for Magento.
A lower end VPS which is untuned and unoptimized will perform even slower than shared hosting services which are properly optimized for Magento.
I noticed this a lot as well. I think its the amount of Ram thats needed that pushes the limit.
I ended up switching to a magento hosting company to sort that out for me, which cost a bit more but removed some of the hassles.
I hope its something they sort for Magento 2.
I disagree. a VPS can very much perfom as good as a dedicated server. It's just the matter of good provider and right setup. With caching and right Mysql setup, it can be done cheaply on a VPS.
I recommend Linode and Rackspace. I heard Digital Ocean is also a decent VPS provider.
probably you need to configure your services properly, and run profiler.