How much solid state device do you need vs. want?

I have been getting asked by IT customers, VAR’s and even vendors how much solid state device (SSD) storage is needed or should be installed to address IO performance needs to which my standard answer is it depends.

I also am also being asked if there is rule of thumb (RUT) of how much SSD you should have either in terms of the number of devices or a percentage; IMHO, the answer is it depends. Sure, there are different RUTs floating around based on different environments, applications, workloads however are they applicable to your needs.

What I would recommend is instead of focusing on percentages, RUTs, or other SWAG estimate’s or PIROMA calculations, look at your current environment and decide where the activity or issues are. If you know how many fast hard disk drives (HDD) are needed to get to a certain performance level and amount of used capacity that is a good starting point.

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