I have a Dell PowerEdge 2900 Server with Microsoft Windows Server 2003 R2 Standard Edition SP2. Storage is RAID 5 consisting of 5 x 146GB SAS (10,000rpm) 3.5 inch Hard Drives. I am slowly running low on disk space and have 3 slots spare at the front. How easy is it to add 3 new drives to the system without losing any of the data currently on the server? I assume I would need to purchase 146GB drives?

It is easy to add storage. Not easy to include in raid normally. Also consider quota's. I read it wrong and answer it wrong too. So get off my case you peanut.

Please don't take this personal but the first mistake is you have no hot spares. In that setup I would have two hot spares minimum with 6 drives in a raid5 array. Second mistake is you should separate OS from data. Usually a mirrored OS and a raided array for programs/data. Usual raid config from dell is two partitions on a single raid array. Very difficult to repair, change or expand. It can be done with careful planning. Reason to separate is if you lose one you still have the other. If disk space is your only issue I would recommend three 500gig drives or if money is a crunch (1) 146gig and (2) 500 gig drives. Reason for all three being 500gig is if you lose a drive in either array you have a hot spare for both. You would mirror [raid1] the two 500gig drives. You could use a junction point [folder that is really the 500gig drive] or just start storing data there. IMO mirrored is better for the pagefile than a raid5 array so there is also something you can move to the 500gig array. Imagine the power of knowing how to internet search http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/FindInfo.html

you can add another drive and expand the array. You can not mix sata and sas on the same backplane. You will have to use a repartition tool to get it all in the same partition

Install DSM on your server if it is not already installed. Buy the hard drives you need and slap them in the server. Use DSM to expand the array using the new drives you just put in the server. This step can take several hours. This will only make the disk space available to server, it does not add disk space to any drives. At this point there is a DOS utility you can download from Dell that you can then add the additional space to any partition that you would like. Don't remember what the utility is called, but if you call Dell they can walk you through the whole thing. It's pretty easy...just takes some time to do.

Thank you all for your replies. To update, the operating system is separted from the data. Therefore, the D drive where the data and some programs are located is what I want to expand with the additional drives. I will also give Dell a call as suggested before commencing.