I was just wondering how many hard drives you can put in a single backup server running Fedora 2?

Thanks,
Jamie

Linux does not put arbitrary limits on the number of hard disks.

With IDE, ATAPI, ATA or SATA drives, you are limited to two disks per channel (master and slave), and usually two channels per controller. But you can still install extra controllers as expansion cards.

With SCSI drives, you can daisy-chain more devices on a single controller (Googling for this, I think 6 might be the typical limit, but you may be able to get more than that on some controllers). Again, you can get additional controllers.

With USB, you can attach as many devices as you like, up to a few hundred per controller given enough powered hubs. Again, you can buy more controllers if you like, but note that the bandwidth is split between all the disks on one controller (and USB hard disks don't tend to have a good size*speed/price ratio).

Inside the kernel, the settings for each device are stored as a vector of device nodes (If I remember rightly), so you even can have as many devices as you like running from the same driver inside the kernel.

In practice, the limits are likely to be the cooling power of your computer (I'd recommend hard-disk coolers if you're running many drives, especially in a smaller box), and the limits of your computer's power supply.

To put more than a few dozen drives in a single box, you may also need to create more nodes in the /dev/ filesystem before Fedora will see them. Alternatively, you could use a hardware RAID controller to combine them into a single device.

You can also have as many software RAID partitions as you like.

Hope that helps,

— Robert J. Lee

So I can put as many usb drives as I want on my server right?

Thanks,
Jamie

i think there is a limit of 128 devices with usb v1 (don't know about v2).
sure you'll get bandwidth problems with a lot of drives.

sl mritch.

Also, note that devices include the number of hubs (and the host controller as well, I think). Hubs only tend to go up to eight or so devices. USB v.2 is faster (possibly comparable to ATAPI with one device at a guess, and 1/n of that speed with n drives)

If you want lots of storage space, you're probably better off looking at SCSI (or ATAPI if money is also an issue).

You could also look at setting up disk partitions if you just want to see a large numbers of small “drives” in software. (By the way, you can use software-raid on partitions as well as physical drives).

Well, we now have 25+ hard drives on one machine and are continuing to add more. We are trying to set up a nightly back up for every employee that we have here on their own 120 Gig hard drive. So far so good, let me know of anymore information that might be useful to me.

Thanks,
Jamie