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I have a home server, with the following:

My goal is to add drives to the server as needed to increase available space. When my case reaches its drive capacity, I will replace the smaller drives with new, larger drives. For instance, suppose my case had four drive bays. In order to add a new, 3TB drive, I'd need to replace one of the 1TB drives with the 3TB.

My ideal end state is:

  • Ability to add additional drives
  • Ability to replace smaller drives with larger drives
  • Fault tolerance
  • As little proprietary technology as possible

I am currently using windows spanned volumes, but I do not know how well it will work when I want to replace a smaller drive.

Any suggestions?

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migrated from Jul 28 '11 at 14:32

This question came from our site for system and network administrators.

up vote 2 down vote accepted
  • RAID is not a backup (so take a backup)
  • 2TB and larger drives have much higher failure rates than 1TB
  • you don't really want anything larger than 4x2TB in RAID5 because chances of a 2nd drive failure during a rebuild become quite high. (More drives is much better than larger drives)
  • RAID1 from one hardware device can usually be moved straight to another and if not splitting it gives you the data on a single drive
  • Hardware RAID reduces IO over software RAID so choose it where available
  • RAID can put more stress on drives especially when left running 24/7. Consider Enterprise/RAID versions

So in summary. Larger drives increase your chances of data loss so make good backups/don't expand too quickly. RAID1 is a good compromise of portability and safety. RAID5 is OK but reaching the end of it's usefulness.

Spanned volumes have no fault tolerance and if one of your drives fails you will lose the whole lot of data. These should only be used where you need particularly speedy access and can afford to lose the data. If you are using windows for RAID you really want to be using mirrored volumes.

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Backup is not truly necessary. This is not vital data. I can buy a controller if necessary... Is JBOD my only option to be able to replace smaller drives with larger drives? If that's even a possibility. – Mike Christiansen Jul 28 '11 at 15:09
Yeah, just don't use spanning. With RAID1 mirroring you simply replace 1 drive, reestablish the mirror, replace the other drive, resize or make a new partition. With RAID5 you replace 1 drive at a time, each time causes a rebuild, then most controllers will allow you to expand the array, then resize/add partition – JamesRyan Jul 29 '11 at 8:37
I understand how RAID works. I'm looking for a solution that will allow me to replace a smaller drive with a larger drive, then allow me to utilize the space. As I understand it, with most (if not all) RAID controllers, if I have 2x 1TB drives, and 2x 2TB drives, if I replace a 1TB with a 3TB, the RAID array will still be the same size. Is there an implementation that will allow me to perform this functionality? – Mike Christiansen Jul 30 '11 at 18:51
please reread what I wrote, you replace each drive in turn with a larger drive, once they are all bigger drives then you can expand the array to fill the space. So if you have 2 arrays, one 2x1TB and one 2x2TB you will need to replace both 1TB drives with 3TB drives – JamesRyan Jul 30 '11 at 22:38
This is a standard thing among all RAID controllers? Or is it a feature set specific to a specific brand, etc? – Mike Christiansen Jul 31 '11 at 15:15

You didn't mention what software you want to run on this "server". If it's just serving files, I'd definitely switch to a different OS, like FreeNAS. It includes the ZFS file system.

One major benefit of ZFS is you can pop 2 1TB drives in the server now, and mirror them for redundancy. Then when that's full add more drives and increase the original pool (no messing with new drive letters, splitting files between various drives, or anything complicated at all; easy easy easy).

FreeNAS is based on FreeBSD; so almost all of the Ports will run in it as well. It comes with a pretty good GUI and Web Interface to make administration a breeze. It will not run Windows program however. FreeNAS can also be installed on a small UFD or CF card, so you can use the 'storage' drives exclusively for storage.

As for the drives. Most companies now make AV drives, which are consumer grade drives made to run 24x7. Most HDs don't mind running continuously in the first place (the heat cycle of turning on is what "gets" them), but the AV drives have a bit of the Enterprise technology sprinkled in for extra security margin.

As for size; most of the newer generation drives have URE of 10^14 or better; do pay attention when selecting drives, it only matters when it matters most. Almost all computers easily support 2TB drives and smaller; 3TB drives are only supported in some of the newest computers.

As others have pointed out hardware RAID HBAs are generally very fast and offload some CPU load. But they abstract drive failure from the OS. If you're using an OS that supports ZFS you want to avoid RAID HBAs as ZFS shouldn't use them.

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FreeNAS looks good to me. Might need to test this out with some virtual machines. – Mike Christiansen Jul 28 '11 at 15:26
FreeNAS would also be my recommendation. If you aren't a linux buff, the initial learning curve can sometimes be intimidating, but the documentation and tutorials on the internet are abundant. It is just a matter of weeding out the suck tutorials. I personally recommend the SmallNetBuilder website. – surfasb Jul 28 '11 at 18:09

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This wont work as spanning has no raid capabilities. You would need to either backup and restore the data to the new drive or shrink the partition down to free up the space. I suspect neither is a viable option as you have probably filled the drive already.

You could but a cheap external caddy and copy the data to the new drive (3TB), blow the span away and then replace one of the drives with the single larger one.

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Im actually only at about 3TB / 6TB. I'm not intending this to be a "backup", just fault tolerance. Buying a 3TB drive and moving everything to it and blowing the span is also not an option. My case has quite a few bays - I wont be replacing the smaller drives until I have close to 12 TB or more, which is not feasible to use this method. – Mike Christiansen Jul 28 '11 at 15:02

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