SQL Server has encountered occurences of I/O requests taking longer than 15 seconds
This is far less often a disk issue, and far more often a networking issue. You know, the N in SAN?

If you go to your SAN team and start talking about the disks being slow, they're gonna show you a fancy graph with 0 millisecond latency on it and then point a stapler at you.

Instead, ask them about the network path to the SAN. Get speeds, if it's multipathed, etc. Get numbers from them about the speeds you should be seeing. Ask if they have benchmarks from when the servers were set up.

Then you can use Crystal Disk Mark or diskpd to validate those speeds. If they don't line up, again, it's most likely the networking.

You should also search your error log for messages that contain "FlushCache" and "saturation", because those can also be signs of network contention.

One thing you can do to avoid those things as a DBA is make sure that your maintenance and any other data-heavy tasks (like ETL) aren't going on at the same time. That can definitely put a lot of pressure on storage networking.

You may also want to check the answers here for more suggestions: Slow checkpoint and 15 second I/O warnings on flash storage

I blogged about a similar topic here: From The Server To The SAN