Still need a few details here.
- What is the purpose of the server? Are they simply file servers? Are you hosting Active Directory, Exchange, MS SQL? Are you running a web server, database server, internally developed applications?
- Rack mount? If this is for a small office, you might go with a tower server rather than a rack mount unit.
- What exactly are you looking for in "fault tolerant"? Do you want users to never know that one server encountered a problem? Should it be on a transaction level or should the users just be prompted to try their action again?
- What operating system do you require? Microsoft Windows, Sun Solaris, Red Hat Linux, Suse Linux, BSD, etc...?
- What type of backup are you looking for? Do you want a local tape drive where the admin will swap tapes manually? Are you looking for a tape library or robotic tape system? Do you want an online archive service? Are you backing up small frequently changing files, large infrequently changing files, etc...? Will the servers be running 24/7 and need a specialized backup solution to handle open files?
- Do you require RAID configured drives? I've had servers where the primary OS disk was mirrored and the data disk were RAID 5. I've also had servers where the two internal disk were mirrored and we used redundant fibre channel cards to connect to a redundant pathed disk farm shared by multiple servers with Veritas software to handle application and hardware failover.
We'll need a lot more details in order to provide an adequate answer.
** Edit **
Still not quite enough information to give an exact recommendation but I'll try with what I have.
Mid-Scale server
- Dual processor system with a modern processor
- Windows 2003 Server
- 4 GB RAM (unless you go 64bit and have the software to match...not sure what database and if it would support 64bit MS Windows).
- SATA disk (unless you really want to go high end SCSI disk...but SATA is better "bang for the buck").
- Most servers will include 10/100/1000 NICs. I'd setup a NIC for the users (possibly with failover and load balancing between networks if you like). I'd also dedicate a Gigabit backbone network between your server and the backup device to ensure adequate data transfers.
Configuration:
- I'd mirror the OS volumes with 80-160 GB disk (if only being used for a database you can shrink them a bit)
- I'd use RAID5 for your data disk. This will provide redundancy against a single disk failure without the high cost of mirroring.
- All data files are on the RAID, all apps on the mirror.
- Most databases allow for OS authentication options. I work with Oracle and it allows pass through authentication.
I haven't setup ActiveDirectory before on any large environments (over say 20 users...I've done lab setups primarily) so I can't provide any info on that setup. I'd guess to setup each user with an account and create various roles based on departments, locations, roles in the company (managers, lower level employees).
I'd also recommend breaking out your configuration into two servers rather than one. I'd place your ActiveDirectory on a system separate from your database, that way if you need to reboot your database server you aren't also bringing down your authentication system. You can pick up a relatively cheap system to handle ActiveDirectory for a 30 or so employee environment.
For the DB server, take a look at servers like Dell's PowerEdge 2970 or PowerEdge 2950. For storage, take a look at the various SAN storage (I'd probably avoid NAS storage so you can avoid the drive mapping problems with how Microsoft mounts shares - You need to map a disk as an authenticated user and likely you want your DB to start as a service. You'll find that if your database files are on a Network Attached Storage mount, you need to authenticate as part of a login. Storage Array Network will require software on the server but to the server, the disk will appear as a local device.)