Help: Explain how external HD functions

Discussion in 'Mac Accessories' started by ZeusMutation, Feb 27, 2015.

  1. ZeusMutation, Feb 27, 2015
    Last edited: Feb 27, 2015

    ZeusMutation macrumors newbie

    Feb 25, 2015

    If at all possible I'd love help understanding external hard drive jargon… but, in a "EHD for dummies" kind of way.

    SSD or 7200rpm spinning discs. I get the basic idea, one spins the others don't.

    My EHD Needs/Wants: I plan to connect via Thunderbolt 2
    1. Transfer 10+GB files to and from desktop superfast (or, as fast as I can afford).
    2. Play/Edit 10+GB audio & video files that are on the EHD for use with desktop without lag or image degradation.

    Is there much of a difference between a SSD & the others for my needs? I originally thought of using a LaCie 3TB d2 Thunderbolt 2 External Hard Drive.

    Storage size aside… is there something better out there at a similar price? $399 and under would be my preferred range.

    After researching, I'm more confused than ever with so much computer speak… I'm hoping for simple facts if there are any??

    Thank you

    P.S. If there is a better 7200rpm EHD w/TB2 over the LaCaie I'd like to know.
  2. IHelpId10t5 macrumors 6502

    Nov 28, 2014
    Look at WD Thunderbolt Duo ( You can get the 4TB for about $440 (close to your price range). If you set it to RAID 0 then you get the fastest throughput and all 4TB. Even at RAID 1 it's still Thunderbolt fast, and has redundancy, but will only be 2TB available.

    Whichever drive you choose make sure that you have a good backup strategy in place as well. At a minimum you should have a TimeMachine backup to a different disk, AND a cloud backup service.
  3. ZeusMutation thread starter macrumors newbie

    Feb 25, 2015
    I'm looking to add the EHD with a new 5k iMac. I'm ordering it with 1TB flash storage. Should my TimeMachine backup be on a different external drive? I've logged into iCloud maybe once or twice since being forced (IIRC) to use it. I Think my mail is all that really goes there?

    RAID.. If that's not for insects, I don't know what it is. Lol.

    Thanks for the response!
  4. ColdCase, Feb 28, 2015
    Last edited: Feb 28, 2015

    ColdCase macrumors 68030

    Feb 10, 2008
    Two quality 7200 rpm drives in RAID0 provide about the same data rate as a single SSD.

    I would suggest something like a 4 bay OWC Thunderbay 4. Populated with two 2TB 7200 RPM drives with the longest warranty. Don't use desktop type drives as they are not designed for the vibration of a multibay enclosure. Use the MAC's disk utility to RAID0 the two drives into your working volume. That gives you 4TB of fast durable storage for your libraries that supports real time video and image editing nicely. Add a 4 or 5 TB NAS type drive and buy/use CCC to clone your working RAID0 volume to it as a backup. Add a ~2TB NAS type drive an use it for the Time Machine destination for your internal drive.

    Seagate Constellation ES.3 ST2000NM0033 2TB 7200 RPM (two of these)

    WD WEWD4001FFSX Western Digital Red, one in 4TB, one in 2TB.

    Lots of money, but you will be happy with something like this, and doing it right is not going to be cheap. There are less expensive ways and shortcuts, your choice..
  5. ZeusMutation thread starter macrumors newbie

    Feb 25, 2015
    I did mention "external hard drive for dummies" right? That last post has me scratching my head... do what now? Reads like a foreign language to me.

    I appreciate the help, just totally lost.
  6. ixxx69 macrumors 65816

    Jul 31, 2009
    United States
    For "sustained transfer" speeds, i.e. moving/copying large files from one drive to another, the SSD is going to be about 4-5 times faster. For a typical single hard drive via TB2 (Thunderbolt 2) or USB3, you'd typically see speeds of 80-120MB/s (megabytes per second), where as an SSD, you should see speeds in the 400MB/s range. This doesn't take into account "RAID".

    "RAID" can get very complicated, but it basically means an array of multiple drives, e.g. there's two or more drives in the external unit, and those drives work in conjunction to offer more storage and speed than the drives working separately. It can be a little more technically challenging to set up, so if you really feel like you're in over your head, I would suggest staying away from RAID.

    There are a bunch of different RAID types, e.g. RAID-0, RAID-1, RAID-5, etc.

    RAID-0 (known as "striping") combines typically combines two drives into a single logical unit - i.e. 2 x 1GB drives = 2GB of storage, and it can double the speed - data can be read/written to both drives at the same time (striping).

    RAID-1 (know as "mirroring") mirrors the data to two drives - i.e. 2 x 1GB drives = 1GB of storage - the data is identically copied to both drives at the same time. This is used for "redundancy". If one drive dies, the other drive still has an exact mirror of the data.

    RAID-5 sort of combines RAID-0 and RAID-1 - it uses three or more drives to both combine the storage of the drives and offer data redundancy - i.e. 3 x 1GB drives = ~2GB of storage, but if one drive dies, your data is still safe (the way this works is fascinating, but too technical to explain here). RAID-5 probably isn't relevant to the discussion since a TB2 RAID-5 storage device will be well outside of your budget (or unless you go in a completely different direction and consider a NAS device).

    First, you have to decide whether you're going SSD or traditional HDD route and whether you're going to use RAID. SSD is going to be more expensive than HDD, and RAID is going to be more expensive than no RAID. Secondly, depending on what setup you decide on, it may make more practical sense to stick with a USB3 drive rather than TB.

    Keeping the discussion to within the ballpark of your budget (i.e. we're not talking $1,000 RAID setups here), there's basically four scenarios:

    USB3 HDD. TB2 is a complete waste of money because the bottleneck is the HDD, not the SATA3 interface or the speed of the connection. Expect to average around 100MB/s (maybe a little faster or slower depending on how full/fragmented the drive is).

    USB3 SSD. Performance varies quite a bit based on the drive, but a quality drive should provide ~350-400MB/s. Again, TB may only offer the slightest of advantages, so while you can get a TB SSD, it's not going to offer much over a USB3 SSD.

    TB2 HDD RAID 0 (2 x HDDs). Performance will about double a USB3 HDD to ~200MB/s. USB3 RAID is available, but I would not recommend them - too many reported stability issues.

    TB2 SSD RAID 0 (2 x SSDs). Performance will about double over a single USB SSD to ~700MB/s. Aside from the stability issues of USB3 RAID, the USB3 interface becomes a bottleneck with SSD RAID.

    Performance can vary quite a bit depending on the manufacturer and usage, so all numbers are just ballpark speeds as a way to compare the technologies. If you're considering a device, you should check specifications/reviews for actual performance.
  7. ZeusMutation thread starter macrumors newbie

    Feb 25, 2015
  8. ColdCase macrumors 68030

    Feb 10, 2008
    Hard drive for dummies is a 400 page book.... you need to be more than a dummy to put together a system, and you probably are, or hire someone with the knowledge. There are dozens of trade offs.

    I posted what to buy if you want a good performing storage to match up with an iMac for video editing. Can't be simpler than that.... without getting into 400 pages of description/alternatives.

    If you want to learn more, perhaps first take a look at a hard drive Wiki

    and then perhaps a RAID Wiki

    and then perhaps NAS and DAS wikis.

    By skimming through these wikis you may be able to pick up the knowledge you want.

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