What parameters to look for when choosing a server?

Question

linux

Good afternoon.
In connection with the future expansion of the organization, the question arose of replacing the current servers:
1) a self-assembled PC with Win2k8r2 (Core2duo [email protected], 6GB RAM, P5K-VM motherboard ). The server is running Exchange 2007. Now the memory is 96% full, the CPU rises to 35%, the disk is mostly at 0%, but sometimes it rises to 10%.
2) Self assembled PC with Win2k8r2 ([email protected] up to 3.70GHz 16GB gigabyte ga-h61m-s1 ram ). The server has AD, DHCP, DNS, DFS, MSSQL, Hyper-v with one machine for 1C (file base) and Symantec Endpoint Protection Manager (uses Java). Memory is clogged up to 78%, CPU ~ 30%, Disk sometimes up to 10%.
At the moment, there are about 30 employees. An expansion of another 20 is expected. And I'm not sure that at least the first server with Exchange will withstand such a load.
If I'm still familiar with desktop hardware, I haven't worked with server hardware. From here I have a few questions, what is better:
1) Take one powerful server, put a virtual machine on it and run as many machines as needed in the virtual machine (3 Win servers and one Lin for the web). But the question is, what happens if it suddenly fails? Then it turns out that all services will just stand, but it seems to me that the virtual machine is easier to transfer from one place to another.
2) To take the server for each task. One for Exchange + transfer something from the 2nd server to it, One for AD, DHCP, DNS, DFS, MSSQL, One for 1C and one for Lin. A total of 4 cars. Then, if one machine fails, the rest will work, but will cost more.
It is also often written in configurations that

2x 3.5"
SAS/SATA/SSD or 4x 2.5" SAS/SATA/SSD

How do you get the extra 3 inches in the second case? Due to the fact that 2.5 are located much closer to each other?
And I don't know what to choose. Something from HP , lenovo , Dell is the first thing that came to my mind. Or are there other manufacturers?
Or is it better to buy a motherboard that supports more memory, buy it in addition and that's it?

Answer 1

You have to move everything into a virtual machine. But you will need at least three servers - two for the cluster, and one for organizing shared storage. But four is better - so that there are two storages :-) Ideally, the servers should be selected so that everyone can carry ALL services. This is in case of failure of one of the virtualization hosts - the entire load will fall on the remaining one.
Well, actually, you have two servers - they can perform the role of storage. Then you need two more new servers.
Disks are not needed in virtualization hosts - they can be booted over the network (via iSCSI or PXE directly from storage, for example) or from flash drives. All you need is storage disks. And it is better to put more disks of a smaller volume than fewer disks of a larger volume - this way the load will be better smeared. That is, conditionally, 8 disks of 2 TB each in RAID10 are much more preferable than 4 disks of 4 TB each in the same RAID10.
2.5" form factor disks are almost twice as thin as 3.5" form factor disks :-) Therefore, 2.5" disks can be stuffed more into the basket.
AD, DHCP, DNS - one virtual machine can handle this, these services do not have any load It is desirable to install Windows Server in core mode (without graphics).
In terms of brands, according to our latest calculations, Dell is currently the cheapest. Lenovo is just a dumbass. HP - not a phony, but noticeably more expensive than Dell. Well, you can try to consider options like pc-administrator.ru/. They give a guarantee on their hardware, and it will cost much less than a new one.

Answer 2

Take a couple - three of the same servers, raise any migration / virtualization solution to them, within the solution, create as many virtual machines as you need services.
For example, in the case of DRBD - OCFS2 - PACEMAKER - KVM, you are insured against cutting down and removing any of the servers from the server room - DRBD will provide live replication of all its disks, and Pacemaker will restart the virtual machines on the remaining servers.

Answer 3

IMHO it is better to take 1 server
1) You can actually move resources between servers
2) tasks will change over time - it will be easier to adapt to new tasks and loads
3) Exchange - they do not recommend using virtualization for databases (but I have a year without failures) true infection eats well, but does not affect the operation of other servers, although the Armenian Radio
option is also not bad, but in taste and color ....