Once you've gone through a few computers, you probably have more than a few old hard drives lying around. You don't have to let them go to waste, though! Here's how to combine multiple hard drives into one, huge volume that'll hold just about anything.
Storage is pretty cheap these days, and buying a new hard drive is always going to be the best way to increase your storage. However, maybe you're on a strict budget and can't afford a new drive. In that case, you might be better off combining some old drives you have lying around. Or, maybe you have other specific needs that require lots of space on one volume. For example, perhaps you're:
- You're storing terabytes worth of of movies, TV shows, music, or other media you've ripped and want it all on one volume
- You need lots of consecutive storage for video editing, photo editing, or other "scratch disk" needs
- You have a lot of games that have to be stored on the same volume (e.g., Steam games) but can't fit them all on one drive
In this guide, we'll discuss three options for combining multiple hard drives, how to do each, and their advantages and disadvantages to one another.
Option One: Use Symbolic Links
By far the easiest method is to use symbolic links, which are similar to shortcuts, but "fool" your system into thinking its the actual folder it links to. So, this allows you to store a folder on your second drive, create a symbolic link to it on your first drive, and it'll feel like all the files are on that first drive (even though they aren't). And, unlike shortcuts, programs on your computer won't know that one folder isn't the real deal. Let's take the video game example from above: Steam requires all your games to reside on the same drive, but if you have more games than can fit on one drive, you can move some of them to a second drive and set up symbolic links on the first drive so Steam is none the wiser.
To do this in Windows:
- Find one of the folders that you want to move to your second drive. In this case, let's say it's
C:\Games\Steam\steamapps\common\Portal. Move that folder to your second drive, and note its location (in this case, we'll say it's D:\Games\Portal.
- Open up the Start menu and type
cmd. Press Enter to open up a Command Prompt window.
- Type the following command and press Enter:
mklink /J C:\Games\Steam\steamapps\common\Portal D:\Games\Portal
Notice that the first path is the location of the link, and the second path is the location of the moved folder. Obviously, replace the two file paths with the paths on your system.
If you were creating a hard link to a file instead of a folder, you would use /H instead of /J after the command.
- Reopen Steam and try to launch your game. It will look in the old path, find the hard link, and be directed to the game's new location.
To do this in OS X:
- Find one of the folders that you want to move to your second drive. In this case, let's say it's
/Users/yourusername/Library/Application Support/Steam/SteamApps/common/Portal. Move that folder to your second drive, and note its location (in this case, we'll say it's /Volumes/Games/Portal).
- Open up a Terminal window (through /Applications/Utilities/Terminal).
- Type the following command and press Enter:
ln -s /Volumes/Games/Portal "/Users/yourusername/Library/Application Support/Steam/SteamApps/common/Portal"
Notice that the first path is the location of the moved folder, and the second path is the location of the link. Obviously, replace the two file paths with the paths on your system.
- Reopen Steam and try to launch your game. It will look in the old path, find the hard link, and be directed to the game's new location.
Of course, you can also perform this function on just about any OS out there,
including Linux. Windows users can also
mount an entire drive to a folder using built-in Windows features. Search around for instructions on your specific OS for more information.
Pros: This method's biggest advantage is that it's easy, and allows you to control the location of each specific file or folder. It works with any number of drives of any capacity and speed. If one of your drives fails, you only lose the data on that drive, and the other drives stay intact.
Cons: If you need to do this with a lot of files or folders, it can get to be very tedious and annoying. If you're storing hundreds of videos (like movies and TV shows), this probably wouldn't be optimal.
Option Two: Create a Spanned Volume
If you have a lot of files and folders to work with and you want them all on one volume (and symbolic links aren't ideal), you have another option: creating a spanned volume (also known as disk concatenation). Spanned volumes are like the opposite of partitioning: you create one volume that starts at the beginning of your first disk, and ends at the end of your last disk, creating one giant volume. This is often also referred to as Just a Bunch of Disks (JBOD). There's a lot of controversy over whether it is actually correct to call it this, so we won't use it here—just know that elsewhere around the net, you may see these two terms used interchangeably.
To create a spanned volume in Windows:
- Back up any data on your drives, since you'll need to erase the ones you're spanning.
- Open the Start menu and type
diskmgmt.msc. Click on the option that appears and find the disks you want to combine.
- If your disks have data on them, right-click on each and choose "Delete Volume." Make sure you're deleting the correct volumes!
- Right-click on the first of the now-empty drives you want to add to your span and choose "Create New Spanned Volume."
- When the New Spanned Volume wizard starts, click Next until you get to the Select Disks screen. Highlight the second disk you want to add to the span, then click the Add button. Continue this process until all the disks you want are on the right size of the selection wizard, then click Next.
- Assign your spanned volume a drive letter, then click Next. Format it as NTFS and give it a name. When it's finished, you're ready to use your new spanned volume.
To create a spanned volume in OS X:
- Back up any data on your drives, since you'll need to erase the ones you're spanning.
- Open up /Applications/Utilities/Disk Utility and click on one of the drives you're going to use. Head to the "Erase" tab, choose "Mac OS Extended (Journaled)" from the dropdown menu, and click Erase. Repeat this process for the other drives you want to include in the span.
- Click on one of the now-empty drives you're going to use, and click the "RAID" tab. Give your set of disks a name, choose "Mac OS Extended (Journaled) as the format, and choose "Concatenated Disk Set" for "RAID type."
- Click the plus sign to add the array to the list.
- Drag your hard drives one-by-one from Disk Utility's left sidebar into the right pane, under the disk set you just created. When all the disks are in place, click Create to create the spanned volume.
Spanned volumes are a little different in every operating system, but the process is similar. Linux users can use
a feature called Logical Volume Management, and most other OSes should have an option for this too—heck,
even Nas4Free has it built right in. Google your own OS for instructions on how to perform similar functions (and remember, it might be referred to as JBOD or disk concatenation).
Pros: Managing a spanned volume is much easier than managing symbolic links, since once you've created it, you don't actually have to "manage" anything. It just shows up on your computer as one big drive. When it runs out of space on the first physical disk, it moves onto the second without you having to worry about it. This also works with any number of drives at any combination of speeds, unlike RAID.
Cons: The biggest problem with spanned volumes is that they introduce a greater probability of drive failure. If you have a volume spanned over three drives, that's three drives that could fail instead of just one, and if one of your drives fails, you lose
all of the data in that spanned volume (though some of it
may be recoverable).
As such, we don't recommend this option for most scenarios. However, if you have a lot of data that isn't particularly important—or is backed up elsewhere (like a bunch of DVDs and Blu-Ray discs that you've ripped)—this might be an okay option. Just be aware of the downsides and the necessary precautions to keep your data safe.
Option Three: Set Up a RAID Array
The last option is using a Redundant Array of Independent Disks, also known as
RAID. It offers a lot of benefits that disk spanning doesn't, like speed, reliability, and protection against drive failure. There are a number of different types of RAID, though, and they each serve slightly different purposes. Here are the most common:
- RAID 0 is similar to a spanned volume: its main goal is to combine multiple drives into one big volume. However, instead of spanning your volumes, it uses something calledstriping: instead of filling up one drive and moving onto the next, it writes data across all of your drives. This means read speeds are faster than a spanned volume, since you can read multiple parts of the data at one time. However, if one drive fails, then you lose all your data with little hope of recovery.
- RAID 1 doesn't actually combine multiple disks into one big volume at all. Instead, it implements a concept called mirroring: Whenever your main drive is written to, your computer writes the same data to your second drive. Your second drive is a mirror of your first one so that if one fails, you can pick right up with the second drive as if nothing went wrong.
- RAID 10 combines the best of RAID 0 and RAID 1: you create a mirrored RAID 1 array, then combine that with other RAID 1 arrays for one big, mirrored volume. This type of RAID requires quite a few disks (two to combine and another two to mirror, at the minimum), so it can be quite costly.
- RAID 5 introduces a feature called parity, which is another method for keeping your data protected from drive failure. Unlike RAID 10, in which you need to use half of your drives for redundancy, RAID 5 can store that recovery data in much smaller parity bits, spread across your drives. That means you can use more of your drives for data and hopefully save a bit of money. RAID 5 will be much slower to write data than RAID 10, though, so there is a tradeoff.
These aren't the only types of RAID, but they are the most common. We could do a whole set of features on each type of RAID, so we won't go into a ton of detail here, but you get the general concept: with RAID 10 or RAID 5, you can expand a volume across multiple disks without worrying about an increased risk of failure, as you would with disk spanning.
There are a number of ways to set up a RAID array. You can use software RAID, which is built-in to many motherboards and follows very similar instructions to creating a spanned volume (you would just choose a striped, mirrored, or RAID 5 array instead). Many people argue that hardware RAID, however, is more reliable, which involves installing a RAID card into your PC and setting up RAID using that. The process varies from computer to computer and from RAID card to RAID card, but
our guide to RAID mirroring should help get you started if you're interested. Windows 8 users might also check out the
new Storage Spaces feature, which isn't RAID, but has a lot of similar goals and features.
Pros: Higher levels of RAID offer the ability to turn multiple drives into one, big, often fast volume without worrying about losing your data. RAID is not a replacement for backup, but it does make your life a lot easier if one of those drives fails. RAID 0 does not provide this redundancy, but is still faster than a spanned volume.
Cons: Unfortunately, RAID has a few downsides too. To start, higher levels of RAID can be expensive, since you need quite a few drives to pull it off. They'd also have to be the same size and speed, or you'd have to sacrifice some of their size and speed. That is, in a RAID array, you're stuck using the smallest disk's capacity for each drive, and the slowest disk's speed for each drive. As such, it isn't ideal if you have a bunch of disks lying around and you're trying to save some money. But, if your data is important, it can help keep that data safe, too. RAID 0's biggest downside is not only the lack of redundancy, but the fact that if you lose one drive, you lose all your data—with little to no hope of recovering it.
Combining multiple disks into one volume is a fairly controversial practice, as it can increase the risk of drives failing. However, if the situation is right—that is, if your data is unimportant, if you have it all backed up, or if you have redundancy built-in—combining those drives can be pretty handy.
