Consider not using Linux (raid). Get an Adaptec SAS card.... which allows you to do a lot more than what you intend.
Anyhow, it can:
- Handle automatic failover to a reserve disc
- Handle regular spin ups to make sure the discs work
- Handle regular validation of the complete RAID
All that keeps the items running properly. Plus you can scale to around 190 discs in cascaded SAS enclosures should the need arise ;)
Consider using RAID 6, not RAID 10 - gives you better performance for more discs than 4, and... well, if that is an archive, anything else is not really needed. Raid 10 is more for high end database servers.
Depending on the size of the RAID, spin up may be problematic during the day. You may not be properly able to spin up all discs at the same time.... and if you stagger the spin ups (can Linux do that?) it may take longer to acutally get them all operational than users may like. Under this case it may be advisable to keep the discs spinning during the day. If that is a new server, for power saving, consider 2.5" discs. Supermicro has a nice cace tha tis 1 rack units and has space for 24 hard discs 2.5" - and a lot more for 3.5", up o 48 or so in one case.