How To Combine Multiple Hard Drives Into One Volume

Once you've owned a few computers, chances are you'll have some 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 can hold just about anything.

Storage is relatively cheap these days, and buying a new hard drive is always going to be the best way to increase your storage. However, if you're on a strict budget and don't want to waste drives you already have, combining those drives in a single volume make sense. Other reasons you might want to do that include:

  • 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" requirements
  • You have a lot of games that have to be stored on the same volume (such as Steam games) and 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 (also known as "hard links"), which are similar to shortcuts, but "fool" your system into thinking the shortcut is the actual folder it links to. This allows you to store a folder on your second drive, create a symbolic link to it on your first drive, and have it feel like all the files are on that first drive (even though they aren't). 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:

  1. 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.
  2. Open up the Start menu and type cmd. Press Enter to open up a Command Prompt window.
  3. 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.

  4. 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.

You can also use free software such as Link Shell Extension (or, in the case of video games, Steam Mover) to perform the same task without the command line.

To do this in Mac OS X:

  1. 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).
  2. Open up a Terminal window (through /Applications/Utilities/Terminal).
  3. 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.

  4. 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.

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 (such as 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,, 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:

  1. Back up any data on your drives, since you'll need to erase the ones you're spanning.
  2. Open the Start menu and type diskmgmt.msc. Click on the option that appears and find the disks you want to combine.
  3. If your disks have data on them, right-click on each and choose "Delete Volume." Make sure you're deleting the correct volumes!
  4. Right-click on the first of the now-empty drives you want to add to your span and choose "Create New Spanned Volume."
  5. 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.
  6. 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 Mac OS X:

  1. Back up any data on your drives, since you'll need to erase the ones you're spanning.
  2. 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.
  3. 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".
  4. Click the plus sign to add the array to the list.
  5. 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 OK 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 called striping: 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 all the recovery data on one drive. 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 lot 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 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. 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.


Comments

    Setup a RAID Array.... Redundant Array of Independent Disks Array?
    Is it somehow better to setup an Array of Arrays?

      +1

        There's a button for +1's right next to the Reply button you clicked.

          You can't do that unless you create account/log in. He is a guest... which is displayed next to his display name.

          Ah but they have a guest account, therefore they cannot +1 a post!

      I guess you also hate it when people go and get cash from the ATM machine?

      That's basically what RAID 10 is, a RAID 1 array that mirrors a RAID 0 array (might be the other way around, I'm never sure). But if you mean like a RAID 0 made up of more RAID 0 volumes then no that's slower because the computer would have to calculate more stuff about where it's writing what pieces of data.

    With Windows 8 you have another option "Storage Spaces".

    This allows you to thin provision any amount of storage you feel you'll need, across an array or pool of drives. This allows you to add storage as you need as well, while the other options (except for the Sym Links) are a bit more rigid.

    I've been using FlexRAID for a while and it is quite good.

    My system for older videos&movies is to file the by decade, then by year. Then a decade like [1990-99] can be moved to a linked drive. I tried this with music, but iTunes shook its fist and demanded all music be sorted by artist... linking music [sorted by artist] to an external source [sorted by year] would be a task for a better programmer than I.

    If you feel the need to run defrag software often, Some software gets upset at Spanned Volumes. Heck, some defragging software gets upset at soft or hard links.
    Not having a RAID, I don't know how assorted defrag programs react to defragging one.

    Are windows soft & hard links the same as Linux soft & hard links? Can you soft/hard link to a volume mounted across a network? There's room for another article here.

    Last edited 27/02/13 11:26 am

    Is it just me, or is there something wrong with the Raid 10 description? It doesn't make sense to me.

    Raid is dead - http://h30565.www3.hp.com/t5/Feature-Articles/RAID-Is-Dead-Long-Live-RAID/ba-p/1422
    I've switched to ZFS (on linux) myself.

    I couldn't help but post on this one.

    !DO NOT DO THIS IF YOUR DATA IS VALUABLE!

    Seriously, once a HDD fails you will loose allot to all of your data and expensive recovery processes ($350ish for a single drive) rarely produce much fruit.
    This is only a good idea as a backup drive. The odds of one of these failing at the same time as a primary drive are non existent (ignoring things like lightning strikes).

    Or just use LVM ( https://en.wikipedia.org/wiki/Logical_volume_management ) under GNU/Linux

    There are only two options not Three.
    Option one is to link the drives to look like one volume.
    Option two is to create a RAID ether in software in the OS (Option two above) or create a RAID in a more basic level on a RAID controller (Option three above) with Hardware or software options.

    If you know everything about RAID and can trouble shoot and recover all issues, use it as you see fit, for everyone else RAID is expensive and risky. RAID works when set up right (Disks & HW) and being monitored but if not it may work for a while then it becomes a PITA.

    Most Types of RAID support one drive failing.... If you have the replacement disk ready to swap in quickly, that works out okay but when one drive fails its just as likely that the next drive may fail in seconds to days of the first, so if you are not prepared you could loose the whole drive. This is where the quality and age of the drive comes in. RAID adds another point of failure also, the RAID controller, this is not mentioned on many redundancy drive calculations ether.

    Don't use RAID for your Boot OS, this was done in the past because RAID offered a Speed advantage but these days, just use a SSD. SSD in RAID you say? you might hit the bottle neck of SATA3 controller on the PCIe bus before you get more speed advantage. Plus it's a pain to configure initially and generally a pain to support later on.

    Simply put, don't use RAID unless you really need >4TB on a single disk and drive linking is not an option. Hard drive manufactures create more robust versions of their hard drives for RAID and they cost more to buy for that reason. i.e. it is not recommended to use the cheap "Green" type drives for RAID.

    I hope this helps anyone thinking RAID is a good idea for their stack of left over hard drives.

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