“SQL Server is slow.”
We’ve all heard it. But that doesn’t always mean SQL Server is the problem. And “slow” means nothing without context and ability to verify.
More often than you’d think, poor performance is rooted in the one thing most sysadmins don’t touch until it’s on fire: the disk subsystem.
There are other potential causes as well, such as choosing the wrong RAID array format (like, say, RAID 6 for your extremely busy log files) and limited bandwidth to a SAN. Note that Kevin’s listings for what constitutes acceptable disk focuses primarily on on-premises solutions, maybe biased toward direct attached storage versus a SAN. For cloud databases, spikes of 30-60 seconds are perfectly fine, of course.