Recommended IO Limit for SSD

[paulo.letigio]

What is the recommended IO Limit that you can set on your Hosting Packages if your server is using SSD.

I want to take advantage of high IO of SSDs.

Thanks.

[sqh]

I have the same question for regular hard disk drives, but have never been able to get a good answer. I realize it is very subjective, but I have never been told how to even try to figure out what is the best setting for our environment. It comes with a 1024 kbps default limit and we have been using that, for lack of any better guidance.

[clm]

There isn a correct answer. We have SSDs + Raid 10 over 3 Raid 1 arrays, this gives us enough total speed to allow a limit of 10 or 20MB/s per account.

Most shared hosts will limit between 1 and 5 MB/s

The question is, how many MB/s can you handle ? And how many users will be likely to be using all of thieses MBs, and how often will small files be copied as small files are slower to read and write than large ones.

Choosng the correct disk limit depends on the number of sites you want to host and the total disk speed you have available.

[sqh]

Thanks for the insight, Richard. I completely understand that there isnt a "correct answer". I just do not know how to go about finding the answer. Your comment about most hosts limiting between 1 - 5MB/s is the first helpful info on the topic that Ive ever seen, and I appreciate that. It sounds like we need to do some disk i/o tests to see what speeds are available, and then decide how much to limit each user. Do you have any helpful pointers on that? I am also doing some general "Googling" on the topic.

Thanks again for taking time to comment.

- Scott

[clm]

We have some complète oss that run on vpss limited to 10 mb/s. The way we choose our limit is to set the limit low enough without our average customers noticing. So far with 10 mb/s on our smaller plans we havvent had any complaints or noticed anything slowing down.

Limiting disk io is much the same as limiting cpu. Some hosts only allow 1/8th of a CPU others allow 2 CPUs. Some scripts will need more disk io than others.

Depending on how you market your plans, you could either start with a low limit and increase it if required or à higher limit and reduce it if you keep getting high iowait.

20 mb/s can slow down a whole system if the files are small enough. The new io/s limit thats in beta should help with this when it becomes stable.