Understanding SAN Transactions (IOPs) on an OrcsWeb Cloud Server

Cloud Servers at OrcsWeb use a Storage Area Network (SAN) to store the image of your server.  All reads and writes to the disk on your server are operations that are performed on this SAN device.   These input and output operations (IOPs) are metered to ensure optimal performance on the cloud servers.

The size of an IOP can be as small as 4 kilobytes and as large as 64 kilobytes.  The total operations used for your server for the month will depend on size the files that are read/written to disk and can also be affected by files that are fragmented on the disk.

You can think of an IOP as a bucket that moves data from the SAN to your Cloud Server.  For small files, a smaller bucket is used (4KB).  If you are working with a lot of small files, it could take many trips of the bucket to move the data.  However if you are working with a large file, a larger bucket (64KB) is used.  This allows you to transfer a larger amount of data in the same number of trips.

In most cases, your usage will be a combination of several different bucket sizes over a given period of time.  In order to plan for the number of IOPs you use, you can calculate IOPs on the low and on the upper end.  This will give you an idea of the minimum and maximum amount of IOPs you may use.

As an example, let’s say that you will transfer 500 GB worth of data in one month between the SAN and your server.  With the smallest bucket size of 4 KB the calculation would look like this:

500 GB * 1024 * 1024 / 4  =  131,072,000 IOPs

This formula takes 5 GB, multiples it by 1024 to convert to megabytes, then multiplies it by 1024 again to convert to kilobytes.  Finally, you divide by the 4 KB bucket size to get IOPs. 

At the other end of the scale we use a bucket size of 64 KB:

500 GB * 1024 * 1024 / 64 = 8,192,000 IOPs

Article ID: 363, Created On: 4/22/2013, Modified: 5/22/2013