By relling on Sep 02, 2008
We often get asked, "what is the best configuration for lots of disks" on the ZFS-discuss forum. There is no one answer to this question because you are really trading-off performance, RAS, and space. For a handful of disks, the answer is usually easy to figure out in your head. For a large number of disks, like the 48 disks found on a Sun Fire X4540 server, there are too many permutations to keep straight. If you review a number of my blogs on this subject, you will see that we can model the various aspects of these design trade-offs and compare.
A few years ago, I wrote a tool called RAIDoptimizer, which will do the math for you for all of the possible permutations. I used the output of this tool to build many of the graphs you see in my blogs.
Today, I'm making available a spreadsheet with a sample run of the permutations of a 48-disk system using reasonable modeling defaults. In this run, there are 339 possible permutations for ZFS. The models described in my previous blogs are used to calculate the values. The default values used are not representative of a specific disk, and merely represent ballpark, default values. The exact numbers are not as important as the relationships exposed for when you look at different configurations. Obviously, the tool allows us to change the disk parameters, which are usually available from disk data sheets. But this will get you into the ballpark, and is a suitable starting point for making some trade-off decisions.
For your convenience, I turned on the data filters for the columns so that you can easily filter the results. Many people also sort on the various columns. StarOffice or OpenOffice will let you manipulate the data until the cows come home. Enjoy.