Raid newb with single hard drive

dumb question here… currently have a single hard drive. planning to get more obviously, but money and all…

Is it worth/possible setting up raid with a single disk, or just wait until multiple disks? Is there an implication about losing data that sits on it if i want to do raid later?

It’s not a dumb question. I obviously don’t know how much knowledge/experience you have but you might want to start by looking at Wikipedia and other resources to see what RAID is.

One thing you need to understand is that RAID is not a backup solution, if you have data files that are important to you it’s important not to have them on only one device. A RAID array can protect you to some extent from hard disk failure causing data loss but some RAID levels are really for speed and won’t protect you from hard disk failure.

Here’s my ramblings on RAID.

I think it is possible to have RAID 0 on a single disk but not sure how practical it would be, not sure if it would be possible to add further disks to extend the RAID array. I have never built a RAID system with a single disk.

Considering the other main RAID options I think you would run into problems trying to build a RAID array that expects multiple disks on a single disk. For example RAID 1 (Mirroring) is normally built on at least 2 disks and should one of those disks fail it will run on the remaining disk until you remove and replace the failed disk
What is called JBOD (Just a Bunch Of Disks) might be what you need but I honestly can’t remember much about it other than you can present disks of different sizes as one logical disk, starting with one disk and adding more to extend it may be problematic.

If you are starting out from scratch with only one disk available to you I would suggest waiting until you get hold of at least one more disk, I would also recommend that you purchase disks of the same size as depending on what RAID level you choose you may not get all the storage available to you, some configurations will restrict your array to the size of your smallest disk.

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Thanks, that was a really helpful response. I have no real knowledge about hard drives. I think i will skip raid for now. I had never heard of it until i saw a lot of buzz about it on here :smiley: so i assumed I am missing out… probably still am, but i don’t think i have the need to mirror the data i want to store. thank you for the help :slight_smile:

@rblanchard

RAID stands for Redundant Array of Inexpensive Disks. It enables many smaller, relatively inexpensive disks to be used instead of a Single Large Expensive Disk. RAID involves combining disks to appear as larger volumes and for some types adds the ability to allow for a failed disk. So you need more than one.

  • RAID0 is also known as “Striping”. Two drives minimum, ideally same size. If you have two disks of 2TB they will appear as a single 4TB “disk”. Both disks are used simultaneously so performance may be better than other RAID types. If either of them fails the data is lost.
  • RAID1 is also known as “Mirroring”. Two drives minimum, ideally same size. If you have two disks of 2TB they will appear as a single 2TB “disk”. However both disks will contain exactly the same information. So if one disk fails the data remains on the other disk. When the failed disk is replaced the RAID system rebuilds the data from the good disk onto it.
  • RAID5 is a form of “Striping” but also involves “parity” information shared amongst the disks. You need a minimum of three disks (ideally same size) and will “lose” capacity equivalent of one disk to store the additional parity information. If you have three disks of 2TB they will appear as a single 4TB “disk”. If you have five disks of 2TB they will appear as a single 8TB “disk”. The parity data means that should one of the disks fail the content of the failed disk can be calculated and rebuilt from the remaining drives when the failed disk is replaced. Failure of two disks will result in the loss of the data.

“Ideally same size” means you can use different size disks but the RAID volume will only utilise space on all the disks to the equivalent of the smallest drive. So if you have 3 x 10TB and 1 x 4TB disks in a RAID5 the capacity will only be 12TB - 4 disks x 4TB (=16TB) minus the equivalent of 1 disk x 4TB for parity data (=12TB) - even though the actual total capacity is 34TB.

There are other types but the above are probably the most common ones.

  • JBOD is Just a Bunch Of Disks. A common type of JBOD uses its disks in a Linear fashion. If you have two disks of 2TB they will appear as a single 4TB “disk”. Unlike “Striping” the disks are used in sequence. Disk size does not matter. Using a 4TB and a 2TB and a 1TB disk will give a 7TB volume. When disk 1 is full it will move onto disk 2. If any drive fails the volume is lost but with the correct tools some data may possibly be manually recovered as the data is not split over disks. With JBOD if you have far more storage capacity than data the first disks in the array will get used a lot but some of the disks further down the array may never actually get used much at all.

RAID is not a backup. It is a method that enables the system to remain available (working) in the case of a disk failure (apart from Raid0 and JBOD) whilst the operator replaces the faulty disk.

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