RAIDs, SSDs, iCLOUD & Performance

Posted on by Larry

A  question I am getting more and more these days revolves around something Jerry Thompson asks:

While I am interested in performance and speed between [Thunderbolt and USB 3], I find I am not completely understanding all I need to regarding RAID technology.

Or, as Craig McKenna writes:

[I recently bought] a 120 GB external SSD with Thunderbolt, I’m wondering how you would go about organizing my media.

I’ve spent a lot of time reviewing specific storage products. In this article, I want to take a step back and discuss storage performance in general.


A RAID (Redundant Array of Inexpensive Drives) is a collection of hard drives that create a pool of storage this is both very large and very fast. To the computer, and on your desktop, it looks like a single very big, very fast hard drive. A RAID builds all the drives into a single box with a single connection to the computer. (Yes, you can custom-build a RAID using stand-alone disks, but let’s just keep this simple.)

RAIDs are categorized into “levels,” which describe a combination of speed, redundancy, and price.

NOTE: “Redundancy” is defined as the ability to recover data in the event one, or more, hard drives dies.

For the purposes of this example, let’s assume each of the RAIDs below contains 1 TB drives which transfer data at 100 MB/second. (For comparison, the fastest a single drive can transfer data is around 120 MB/sec assuming it is connected internally to a recent-issue Mac.)

There are other RAID levels – 3, 10, 11, 50 and 60 – but these four are the most relevant to individual video editors. From my point of view, while RAID 6 provides more security, I am happy with the balance of speed vs security of RAID 5, which is what I recommend most.

NOTE: Drobo is a special case. In general, all RAIDS must use drives of the same size and speed. As well, all drives need to be installed at the time you first power up the system. Drobo, on the other hand, has invented a new technology which allows you to add drives, or mix and match drives of different sizes, even after you’ve put the RAID into operation. While Drobo does not provide the fastest RAIDs, this flexibility can be a huge benefit.


This is so cool… This works because all digital data is stored as either a 1 or a 0.

Imagine a 3D checkerboard — let’s make it 5 stories high. Look down on the top left square and count the number of checkers on that square for each of the top four layers.

If they total an odd number, put a checker on the same square on the bottom layer. If they total an even number, don’t put a checker on the same square on the bottom layer.

Now, remove the second layer and all it’s checkers, and put in an empty new checkerboard to take its place. By counting the number of checkers on the remaining top three layers and comparing the total to the indicator on the bottom layer, you can exactly rebuild all the missing checkers on the second layer. For example, if the total of the other three layers is even, and there’s a checker on the bottom layer, add a checker to the new layer. If the total of the other three layers is odd, and there’s a checker on the bottom layer, don’t add a checker to the new layer.

This is exactly how RAID redundancy works. Except each checkerboard represents a hard drive in the RAID. The bottom layer, which provides data redundancy, doesn’t need to know which drive failed, it only needs to compare the totals on all the different hard disks with the total stored on the redundancy disk in the RAID. This technique works whether you have three drives – the minimum – or twenty drives. The only difference is that more drives take longer to count and only one drive can fail at a time.


An SSD (Solid State Drive) drive is essentially RAM that has been configured to act like a regular hard disk. You copy and move files around in it the same as a hard disk. And, unlike RAM, it remembers your data when the power is turned off. Depending upon which version of the operating system you are using, an SSD drive ranges from “so-so” performance to blinding. Later versions of the Mac operating system do a much better job supporting SSD drives.

The big benefit an SSD provides is speed. Its two big limitations are cost and limited storage size.

While you can put an SSD drive anywhere you can put a “normal” hard disk – which we often call “spinning media,” the best place to put an SSD drive is inside your computer as a replacement for your boot drive.

Attaching an SSD drive externally via FireWire 800 will severely limit its performance and is not recommended. You won’t see any significant speed improvement because FireWire 800 is too slow.

NOTE: There is a limitation of SSD, however, in that it only allows a certain number of read/writes before the unit starts to fail. While the overall longevity of SSD is still being determined, for now, assume that you will need to replace an SSD drive sooner than a spinning media drive – probably after 3-4 years of normal use.


iCLOUD, and other Internet services like DropBox and YouSendIt, are essentially file servers that store your files outside of your computer.

If we ignore issues like file security, these services are excellent for backing up data, sharing files between devices, and moving files between computer systems. However, they are not good for storing source media files for editing. It isn’t because they don’t store enough. Just the opposite, these services can store a vast amount of data. The problem is that the connection speed – called the “data transfer rate” – between your computer and the iCloud is too slow. Video editing requires data transfer rates far beyond anything supplied by even the fastest DSL or cable modem.

Use the Cloud for sharing, but not for storing or editing source files.


Thunderbolt is a method for connecting monitors and hard disks to your system. In this regard it is just like FireWire or USB – its a cable and communication protocol that move data to and from your computer and storage.

The big benefit to Thunderbolt is that it is REALLY fast! More than 1 GB/sec of data transfer speed! However, in order for that speed to be realized, you need a REALLY fast RAID. A two-drive RAID 0 won’t begin to fill a Thunderbolt “pipe.”

Thunderbolt is how you connect your drive to your computer. The speed you get will depend upon the speed of the RAID you have attached. Here are some very general expectations for data transfer:

NOTE: A single drive connected via Thunderbolt will be only marginally faster than the same drive connected via Firewire. In order to see significant performance improvement, you’ll need to use a RAID that contains at least four hard disks.


For best performance, I recommend replacing the spinning media hard drive inside your computer – this is also called the boot drive – with an SSD drive.

In general, media should not be stored on your boot drive. This means that only applications and the operating system are stored on the boot drive – along with other files that tend to be small, like email or word processing documents. If you have a large iTunes collection, or large iPhoto library, moving them to an external drive may allow better performance.

If I were setting up a new system, which I am doing next month, I would get a Mac with a SSD drive as the boot drive, and a Thunderbolt RAID 5 drive for media and project files.

My current boot drive uses 148 GB to store all applications and operating system files. I have hundreds of apps which don’t take a lot of storage. So, you don’t need to get a gigantic SSD drive – 250 – 500 GB is more than sufficient.

My media RAID, though, can’t be big enough. I haven’t decided exactly what I’m getting, but I’m looking for 6-10 TB (that’s Terabytes) of storage. I’ve discovered that hard drives have two states: empty or full. I want this one to remain as empty as possible for as long as possible.

This configuration provides a huge speed boost for the operating system and applications, while providing extremely fast access to huge amounts of media, with full redundancy in case of drive failure. This setup also offers a good balance between price and performance.


Here is an article that explains hard disk and RAID performance  and video formats in more detail. I highly recommend you read this article to understand the speeds you can expect from a storage device, how much space it takes to store media, and the data transfer rates of popular video codecs.

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13 Responses to RAIDs, SSDs, iCLOUD & Performance

  1. David Esp says:

    Some further options/perspectives:
    1. Network-Attached Storage (NAS). Too much latency? Further issues? Specialised video ones exist, that avoid these?
    2. eSATA connected drives e.g. GRaid-Mini or Lacie 4Big

    Regarding Thunderbolt, I have read that its speed advantage is much reduced when data is being read-out non-sequentially, as I guess would happen for a project built on a set of video streams (multi-cam, PIP, ..). But if I’ve mis-construed anything there then I would certainly like to know! I have documented my grubby research on such topics at, under title: “USB3, eSATA, Thunderbolt: Comparison: I like the look of eSATA”.

    • Hey David

      Thunderbolt is just an interface (a form of PCI-e). Even within an external Thunderbolt enclosure with one drive, the drive is connected to the Thunderbolt chip via SATA. I believe in your case, it’s not Thunderbolt that’s have difficulty reading out non-sequentially, it’s the drive within the Thunderbolt enclosure. An SSD will be much better at this than a spinning hard drive. Same thing with USB3 enclosures – they connect to their internal drives via SATA. As Larry mentions above, you’ll only see the speed gains of USB3 and Thunderbolt with RAIDs. it should also be mentioned that RAIDs are terrible at reading and writing small files, especially non-sequentially. They are designed for large sequential files like video.

  2. Martin says:

    Larry … I will follow your recommendation as given above! Does the new Fusion Drive announced yesterday reflect your thinking on separating the boot files from the FCPX footage? Are there any product recommendations for a good RAID product on the market or will we see new ones short term ? WD and LaCie have RAID 0 and 1, Promise seems to have issues on product reliability based on users comments in teh Apple Store …

    Thanks for advice as always!

    • G-Technology and Drobo have both announced RAID 5 Thunderbolt products. More will be coming shortly. Apparently, the technology is very hard to implement.

      And, while the Fusion drive is very fast, using two separate drives for video editing still makes a great deal of sense.


  3. Steve says:

    Thanks Larry for this excellent article! It answered all of my questions without me having to go through other forums with hundreds of threads! Best, Steve

  4. Bob Hirschfeld says:

    Hi Larry–

    I don’t earn my living as an editor, and can’t afford to buy a Thunderbolt RAID. I’m looking at a single Toshiba USB3 drive that runs at 5700RPM for $120 at Amazon. Is that going to be a problem? Thanks as always, Bob.

  5. Larry:

    Why is it worth it to spend the money on a RAID-5 (for the redundancy) rather than have a RAID-0 with backup, like with Time Machine?

    • Eric says:

      if a drive fails in your RAID-0, you can’t switch to your Time Machine backup and keep working. You have to restore the Time Machine backup to something before you can use it.

      In my home system, i didn’t want to take up a card slot with a RAID controller. so i have 4 internal drives in a Mac Pro in a RAID-0 for speed, and an external drive backing it up. still not ideal, but if i lose a RAID drive, i can still work off my backup if i need. If i could spare the slot, I would have gone with a RAID controller and RAID-5. Much more reliable.

  6. Kereta sewa shah alam says:

    Everything is very open with a precise explanation of the issues.

    It was definitely informative. Your website is extremely helpful.
    Thank you for sharing!

  7. Carolina Martin says:

    I would appreciate your advice. I’m working on a no budget doc. I have 5 years of content backed up onto two GRAID 0. Just learned it’s not for long term storage so looking to buy new drives. I need about 12 TB of storage for all the content. Leaning on buying 2 and shipping one elsewhere vs. buying one more “dependable” one. Your article is from 2012 but very helpful. Wondering what your advice would be today in my case? Assuming still rec, RAID vs. GDrives? Leaning towards 2x Raid 1 vs. 1 Raid 5 or Raid 6. For the extra cost and research it seems people rec. Raid 6 over 5? Then there’s raid 10 but unclear about the benefit of it. Safety of content is my greatest priority. Please advise. Thank you!

    • Larry says:


      12 TB is far too much media to fit on a single drive. So, a RAID becomes necessary. RAID 1 provides built-in data duplication – but reduces the total storage available. Also, you’d need to purchase multiple RAID 1’s to store all your data. As you’ve discovered, avoid RAID 0. And RAID 10 will be too expensive and well beyond what you need.

      RAID 5 is a good choice – especially because you want to buy two. This is a decision I support.

      12 TB RAID 5 systems are affordable and use very solid technology. 4 TB hard drives – which would be in that system – have been in the market a long time and are as reliable as any hard disk today.

      Look at drives from Promise Technology and OWC; though other brands are also good. Don’t buy a no-name brand just because it is cheaper. You want a company that will be around for a while.


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