I would imagine the HP DL 140 3rd generation, which is what I believe you're referring to, will work fine. However, from the specs, it looks like it comes with quite a complicated set of disk controllers. Almost assuredly, there will be considerable work to do making sure that the controllers are configured in such a way that you are not making a ticking time bomb. But there's forum posts on that.
From memory, the only one that will behave properly with FreeNAS is the SATA non-hotswap version. All of the others won't pass the disks through when left unconfigured.
From memory, the only one that will behave properly with FreeNAS is the SATA non-hotswap version. All of the others won't pass the disks through when left unconfigured.