Migration, backups - how many disks do you need for storage?

Question

Backup

Hi all.
The plans include a cluster of two HPE ProLiant ML350 Gen8 servers. 2*2680V2, 96GB. 100 users in total will work on one server, i.e. 4-5 terminal servers and 5 virtual servers. Interface for connecting storage systems and servers - SAS, probably? SHD model - I focus on HP StorageWorks P2000 G3. I plan to buy storage systems only used. Disks - only new. Budget for storage and disks - $ 2800 - 186,000 rubles. For disks that will be connected to the storage system:
- I plan 1 SSD for terminal servers
- 1 SSD for virtual servers (domain controller, etc.)
SAS disks 2.5 large do not fit the budget, so I plan to choose a regular sata.
- multiple SATA storage for files and hot data in RAID 5
- several sata for storing backups and cold data RAID 6
As a result, the migration of virtual machines between two servers should work. Storage must support SSD. The SSDs themselves are planned by intel, with the Enhanced Power Loss Data Protection function.
Tell me, which disks are better to buy for storage and how many disks do you need?

Answer 1

1 disk generally in any case can not be done. At least 2, in RAID.

Answer 2

I can only say that the MSA 2000 is omnivorous, you can buy sleds on ebay and simple SATA drives, it will eat them. By the number of discs, how many you can buy, take as many, to the maximum.
I have an RDS farm of 6 virtual machines with 32 GB of RAM each, holds up to 50 sessions, more than 50 starts to slow down slowly, when it gets to 70, it gets up with cancer :)
In general, you can only understand by experience whether you have enough disks or not.