Does 10G switches matter more than 10k (over 7.2k) hard drives in terms of improving speed?

Speed has been our concern since we include a SQL ERP in our virtualization project. With that in mind, if we have to pick either 10G switches or 10K (over 7.2k) hard drives which one you suggest matters more? How about more host memory?
Appreciated for your input.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Spindles at 10k, or 15k RPM, they have more IOPS.

7.2k rpm disks should not be used for virtualisation hosts, they are too slow, unless you have Read and Write SSD for cache.

But also, make sure you select the correct RAID groups, e.g. RAID 10, for DB and Logs.

How much memory do you have in your hosts ?

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