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SSD caching performance
I am running a cpanel server with 72 gb memory, files saved in HDD and database in ssd, hosts about 2000 domains with an average load of 2. I am thinking about upgrading the server with ssd caching , and better cpu , i would like to know if the implementation of ssd caching would bring down server load and memory consumption seriously.
Here is the result when i run free -m
Thanks
Comments
No. The OS will still cache stuff as normal - so memory usage won't go down. If you're using software SSD caching, there's also a small memory impact of that - so your memory usage may even go up a little.
Unless you change your settings (vm swappiness, et al), the OS will still manage this for you. Plus, CPanel is a pig unless you spend time optimizing it. Then, it's still a pig (but slightly smaller).
@AnthonySmith can perhaps tell you what you could expect :-).
You have 49G free if any applications actually need it. Cached 33g is the files you want to try and reduce? Memory is still loads faster than sad so it would be with the forest read but all other reads wpould not be effected.
What's the problem you are trying to solve ?
I see nothing wrong with a server with cPanel installed while having a load of 2.0 with 2k sites. Also, the memory appears to be cached, which is not a problem at all, when the servers needs some ram it will just take it from the cached ram.
I would like to know if the server would do fine with less memory [say 32 gb] upon implementing ssd caching, so that the server load will be something around 3, sorry i didnt make it clear in OP. From your post i expect it might work.
Thanks
Yes, in general, but the first thing you absolutely need to know before wasting your time and money is what are your bottlenecks right now.
As has been said a load of 2.0 ish on a cPanel server with 2000 sites is effectively nothing.
An SSD cache wont help you 1 bit if your limiting factor is CPU, similarly an SSD write cache wont help you at all if your biggest overhead is random reads.
Find out what you actually need, it wont bring down ram consumption, but you are not even using all of your ram now anyway so you dont need to worry about that.
Best thing to do is install atop and run atop -d
If you do that and record your screen for 30 minutes or so and send me a link to the video I would be happy to make suggestions based on that as to what you 'actually need'
If an SSD cache is what you need then yes, you will see a marked performance difference, but it will not impact Ram use or CPU much, maybe a little, but not noticeably.
Based on your free -m output, you 'could' get away with 32GB Ram, but your load may go up a bit, right now your commit is around 54GB ((cached(1st line)+used(2nd line))
I'm curious to know if the same configuration of server can handle atleast 1000 wordpress websites with minimum traffic.
Wouldn't it be more beneficial to use something like litespeed to achieve better speed than OS caching ?
@SamP
I suggest you ask again providing the necessary data. depending on the OS "load about 2" can mean "so what? plenty air to breathe" as well as "Don't complain. You are lucky that server is still running".
As some already noted, you have no mem. problem with 49 GB free. But you have a knowledge problem that shows, for instance, in having a swap in your situation.
"better cpu"? Well how many C/Ts do you have now? What else do you run - LAMP? How many req/s dou you have avg and peak? Is your DB mostly read or lots and lots of inserts and updates? Where is /tmp - on spindles, on ssd, or in ram?
The max help you can expect is defined by the info you provide.
Load of 2 means there an average of 2 running processes on the cpu around that moment. On a single core machine that means each process is getting about 50% of the available cycles (i.e. the cpu is overloaded), but on a quad core machine it means only 2 of the cores are really being used.
Worry about the load when it gets above the number of cores.