Raid 0 is the fastest.
But there is a catch, if one of the disks gets messed up, you'll lose everything on both disk!
Since you're building a server, i would go with RAID 1.
RAID 0 - Data distributed on two hard drives, so if we assume that you have two hard drives which are just fast, the speed will be doubled if you run two in RAID0, rather than running them normally.
The risk of losing data is also twice as high as everything is lost if one disk goes.
RAID 1 - All bits are on both hard drives. The most secure solution, but speed is the same as if they do not run with RAID.
RAID 0+1 (mirroring + ping industry) - Combining the two above, where data will not be written alternately on 2 discs and then mirrored on 2 other discs. Requires at least 4 disks, an even number of disks.
Reconstruction is a significant inconvenience stringent process than RAID 1+0, which also gives the same benefits, therefore it is recommended not to use RAID 0+1.
RAID 1+0 (mirroring + industrial ping) - Data become the mirror and then alternately scattered on multiple discs. Requires minimum 4 disks, an even number of disks. Is often used to give all redundancy and performance benefits of RAID 1 and a further gain better speed writing from RAID 0.
RAID 2 - Data distributed on bit level or in very small blocks on multiple disks, and a "Hamming codes" are calculated and stored on one or more parity diskette. Requires at least 3 disks.
RAID 3 and RAID 4 (Not ping dedicated parity) - As RAID 0, but with a disk that is dedicated to, respectively parity bit (RAID 3), or parity block (RAID 4). Parity used for data restoration by the crash of a single disk. Requires minimum 3 disks.
RAID 5 - (Not ping with distributed parity) In RAID 4, but with distributed parity block. Again, the data can be recreated by failure of one disk. Requires minimum 2 disks to work, but typically 3 disks to have any relevance as compared to RAID level 1.
RAID 6 - (Dual industrial ping distributed parity) As RAID 5, but with twice as many parity blocks. Here it is possible to restore data at the crash of two discs. requires minimum 4 disks.
Improving equal to 2 divided by the number of disks.
Performance: As a RAID level 5 minus one disc.
The most secure method used for servers and such as music studios, which lost data is a disaster.