Can I use a PC server as a NAS device?

Dedicated NAS-based storage units tend to be highly optimised for moving data around, and often come with additional functionality such as being an FTP server, a media server, and often incorporate snapshots and replication. Disk access should be easy, and the majority of RAID-based NAS systems will allow hot-replace of disks.

A PC-based system will likely come in much cheaper than a dedicated NAS box, and there are open source options around to create a PC NAS (FreeNAS springs to mind). If you are OK with installing software and have a spare PC lying around, then it is pretty easy to set up.

Remember, even though many PCs come with built in RAID, it will generally only be RAID 1 or 0, and if a greater level of redundancy is required, then a separate RAID card will be required - which will push the cost up a little.

In summary, you can set up a PC to do the job of a NAS device but you'll get what you pay for in terms of features and resiliency and if you have a lot of data you should look at a product dedicated to the job.