VMWare, is it worth changing disks and which ones are better?

Question

Hard disks

Good day.
There is a server: HP ProLiant LD380 G7 (Intel Xeon E5645, 26Gb RAM, 7 HHD HP EG0300FBDBR RAID5). It has VMWare ESXi installed.
It deployed - DC, DHCP, WDS, Mail Server (100+ users), FS (300+ users), Fax server on Elastix and a small internal web service on debian), All disks - Thin Provision.
The warning Device naa.600508b1001c7d66fbd5fdf91dbe37aa performance has deteriorated began to appear daily. I/O latency increased from average value of 1766 microseconds to 35820 microseconds. Yes, and it feels like everything has become slower to work, in this regard, we are considering replacing the HDD with an SSD. But from various discussions and articles a misunderstanding arose:
1 - Do you still need to do a raid for the SSD or set up manual data duplication? Everywhere they write differently.
2 - Should I consider NVMe drives? I'm not sure whether such a high speed is needed and, as I understand it, they cannot be connected into a hardware raid.
3 - If you still take NVMe disks, can they be organized into a software raid using VWWare? And again, is it worth it at all?
4 - Maybe the current disk subsystem can cope with the deployed servers and would you recommend any VMWare settings? Although it's probably hard to advise something, without more details ...

Answer 1

Do you still need to do a raid for the SSD or set up manual data duplication? Everywhere they write differently.

If you need any of the benefits that a raid gives you, you should. For example, make the same mirror.

Should I consider NVMe drives? I'm not sure whether such a high speed is needed and, as I understand it, they cannot be connected into a hardware raid.

It is highly recommended to consider them. But you can get by with others.
It should be remembered that with SSD there are many specifics related to the principles of operation of SSD.
For example, in your case, TRIM will obviously not work - therefore, it will be necessary to leave over provisioning. In your situation, simply replacing the HDD with an SSD can make the situation worse.
It is advisable to calculate and predict the load and take the appropriate SSD.

Answer 2

Nvme in your case is clearly superfluous, since you don’t have a single task that requires super speeds from the disk

Answer 3

ideally, instead of upgrading, I would agree on a new server and smash the services. here the problem is not even an SSD.