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I have a few questions about I/O limit in a hosting package. Lets say a hosting package offers 1MB I/O limit.

  • Does it mean that at any given time no more than 1MB data can be transferred from disk?
  • If I know the average page size (including its files), can I determine by this limit how many concurrent visitors this hosting package can handle?
  • If this limit is reached at any given time, are further requests dropped or delayed?
  • What are other things about I/O limit I should be worried about?

------ After Stephen's answer, I'm adding this graph image from GoDaddy hosting account.

GoDaddy Input/Output graph http://www.imagesup.net/?di=1140434440510

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  • You got me on that one. I have never heard of this. You may need to call a hosting company and ask if there is no answer here. You can answer your own question after 8 hours. If you find something out on your own, please share that with us so that we can all learn something new. Thanks! – closetnoc Jul 2 '14 at 3:10
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    I have a GoDaddy ultimate hosting account. Under resource usage section, there are a few graphs, one of them is about I/O limit. The limit is 1MB, the graph shows that this limit was reached a few times during last 30 days. GoDaddy has removed their support-ticket help system (may be just in my country), so I'm asking it here. – head_scratcher Jul 2 '14 at 6:00
  • @Stephen Ostermiller answer makes sense. Why it is referred to as I/O, is beyond me. This is network bandwidth and not I/O. I say this with about 30 years experience with hardware, OS, and software internals experience with many systems and companies. I have never heard of network bandwidth referred to as I/O. Sorry- I could have answered this easily if I knew what was being referred to. I am glad Stephen Ostermiller was able to come to the rescue! – closetnoc Jul 2 '14 at 16:10
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    For GoDaddy it is not about network bandwidth, but disk I/O. I work with Linux Ultimate packages and I know that they do not limit bandwidth there, but they do limit I/O – rhand Jun 13 '15 at 3:53
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I expect that they mean that the input and output on your network connection is capped at 1Mb/second. (Note the lower case b for Megabits as opposed to a capital B which would mean Megabytes.) Hosting providers often provide a graph of your historical network i/o that looks something like this:

1Mb/second is about 10GB of transfer each day if you are constantly saturating your network connection. Most websites don't use their network consistently and have to have bandwidth available to handle bursts of traffic and more popular times of the day.

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  • Makes sense, but I'm not sure if it is per second. Because there is a table of usage history under graphs. For example one entry says that from 06-09 03:00 to 06-09 04:00 the usage was 935/1024. I have added 30 days graph image to my original post. You can see 1Mb limit was reached a few times. – head_scratcher Jul 2 '14 at 23:53
  • OK, I did not pay attention to the heading of this particular column of the usage history table which says IO(KB/s). And from the graph it is obviously 1MB not 1Mb. – head_scratcher Jul 3 '14 at 0:01
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No it has nothing to do with network traffic. The company I work for has a GoDaddy hosting account, disk IO and network caps are similar in GoDaddy but they are not the same. If you have a PHP script that prints out a simple "hello world" but before printing the hello world, it needs to perform operations internally inside the server that triggers the movement of 20 MB worth of files, then that script will take 20 seconds to load. And that is because of the disk IO limit, it has nothing to do with network(for a realistic test try to echo hello world in a Symfony 2 project on GoDaddy and watch the load time...)

It basically means what it says, they are limiting your disk operations to 1 MB/s, even if those disk operations are not doing any network tasks. A more realistic example is if you are lets say performing a search by filename in a large directory of file, you will not be able to go through more than 1 MB worth of data per second.

GoDaddy limitations are hidden in the terms and conditions

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    +1 GoDaddy does not indicate that they limit disk I/O well at all when you buy a package. They do mention RAM/ CPUs used and that you have unlimited bandwidth and storage on Linux Ultimate godaddy.com/pro/cpanel-hosting?ci=93999 for example, but I/O limitations are hidden, but you will find out when you use certain scripts like backup scripts. – rhand Jun 13 '15 at 3:51
  • Unlimited is a dirty marketing scheme, the speeds are so low, you probably get more with a limited 1 terrabyte package somewhere else than you get with godaddy's "unlimited" If I am not mistaken, they also reserve the right to "throttle" you or ban your account if you are using too much of your "unlimited" resources. – Joe Yahchouchi Jun 15 '15 at 6:44
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Refer below link for exact definition of IO limit as per godaddy.

https://in.godaddy.com/help/how-do-each-of-cpanels-resources-affect-my-site-9323?v=1#io

Quick reference (copied from site):

I/O is short for "input/output." In the context of a hosting account, it's the "throughput" or speed of data transfer between the hard disk and the RAM. Obviously, increasing the speed of transfer makes the process faster.

When Increasing I/O Matter Most

Unlike some other limits, you don't "exceed" your I/O limit and it doesn't generate errors. Instead, a site just "hangs" while it waits for the data to transfer from the hard disk to the RAM.

Knowing when increasing I/O will improve a site requires knowing something about its construction. Generally speaking, sites that need to read and write a lot of data, such as those streaming any kind of media or with many database records, benefit most from I/O enhancements. However, increasing the I/O limit will not fix every issue that cause the site to lag or hang.

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