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  1. #1
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    Shaun(OfTheDead)'s Avatar
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    Two Smaller External Harddrives or One Larger, RAID Enabled Harddrive

    Here's one for you.

    Would it be safer for me to store all my work redundantly onto two, external harddrives, OR singly onto one, large, RAID-enabled harddrive?

    Is RAID all it's cracked up to be?


    I'm shopping around and looking at either buying two 2TB Western Digital or one 4TB Western Digital Quad .


    Any advice?

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  2. #2
    Programming Since 1978 silver trophybronze trophy felgall's Avatar
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    You need at least two hard drives minimum to be able to use RAID and the only option with two drives that provides any benefit is to have one as a complete image of the other. It is only once you have three or more drives that you get any real benefit from RAID as then you only lose one drives space from your total in order to get full protection from any one drive failing.
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    As Felgall says, in both cases you need two drives.
    I had a mix of both strategies:

    1) I had two identical 200GB drives sitting on a RAID card, configured as RAID 1.
    2) Various external drives.

    All the drives are encrypted with Truecrypt.
    I say "had" because one of the 200GB drives failed and couldn't be fixed. I didn't lose any data. At the moment I am considering whether to get another two drives brand new or try to find a similar 200GB drive to re-establish the array.

    In my opinion, backups must be:

    1) Physically remote
    2) An exact copy of the original data

    In a home environment it is not so easy to satisfy both those requirements. Even with my setup (when both drives were okay) a fire in the house would mean loss of data even if I was storing the external drives off site. If you backup onto the external drive after the creation or modification of any data then you'll be ferrying that external drive to and fro from its storage place, which inevitably results in you either not doing that daily backup or you do it but keep the external drive attached. If there's a fire, you've lost it all.

    Another option is storing the data online, but I guess you will then be paying to do so.

  4. #4
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    I'm actually not too familiar with what a RAID is. From my understanding, I thought a RAID already was four drives working in a battery so that if one of the four failed, the other three could restore the data from the one. Is that correct?

    Yes, my first idea was to get two large, identical drives and store the same data onto both as backup (every month, or on completion of a job). Interesting point about them being physically remote, though. My home is my office so I don't see that happening. But I'd still like the peace of mind that if one drive malfunctions, I can recover data somehow.

    Ideas?

    Should I just go with a pair of drives and forget the RAID ?

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  5. #5
    Programming Since 1978 silver trophybronze trophy felgall's Avatar
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    RAID is the process of linking the disks together - you still need the separate drives to implement it.

    Possibly the external RAID box you are considering may have four hard drives in the enclosure but you'd need to read the specifications for it to be sure.
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  6. #6
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    Quote Originally Posted by Shaun(OfTheDead) View Post
    [FONT="Georgia"]I'm actually not too familiar with what a RAID is. From my understanding, I thought a RAID already was four drives working in a battery so that if one of the four failed, the other three could restore the data from the one. Is that correct?
    Not by definition. The minimum number of drives is dependent on what type of RIAD you're using. The most common types are RAID0 and RAID1.
    With RAID0 two separate physical drive are regarded as one large logical drive. The advantage being that when the RAID controller gets an instruction to write it can choose between the two physical drives - it can write to whichever one is more idle. This has a slight (altough IMHO neglectable) performance increase and suffers from the huge problem that if one of the drives crashes, the other one is worthless, since the array only works if both drives work.
    RAID1 is probably what you want here (and what the external HDD you linked to supports). You take 2 drives, where 1 is actually the one that's working, and the other drive is doing nothing else than constantly copying changes from the first drive. So, if one of the drives crashes, the other one can go along as if nothing is wrong.
    RAID1 saved my servers from quite some data loss this last year! (in one array one of the drives crashed, in another first one drive crashed and a month later the other. No data loss though thanks to RAID )

    For more details on RAID read this http://en.wikipedia.org/wiki/RAID
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  7. #7
    Barefoot on the Moon! silver trophy Force Flow's Avatar
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    RAID5 is typically used for redundancy. So, if one drive fails, your data is still there. There are some speed benefits as well. RAID5 is also more common for servers than desktops. Minimum drive requirement is 3, but most folks recommend at least 4 plus a failover/hotswap drive.

    RAID 1 is not a reliable backup option. If one drive fails or the data gets corrupted, it sometimes gets carried over to the second drive. I've seen this first-hand more than a few times. This requires at least 2 drives.

    RAID 1+0 offers spanning and mirroring, though doesn't offer enough redundancy to always survive a failed HDD. 2 drive minimum, 4 recommended.

    RAID 0 offers performance, but doubles your changes of data loss since if either drive in the array dies, you loose everything.

    There's also JBOD, which effectively spans a partition over multiple drives. But, like with RAID 0, if one drive goes, you lose everything.

    So, in addition to the different types of RAID, there's als hardware RAID vs software RAID. Hardware RAID is typically more reliable, less error-prone, has higher throughput, and requires additional hardware to use. Software RAID puts extra load on the CPU, is dependent upon the operating system, and doesn't require a separate piece of hardware.

    A hardware-based RAID array can typically be transplanted into another computer without trouble. In most cases, a software-based RAID array cannot.


    So, bottom line, hardware RAID5 is usually best for performance and redundancy on an active computer using RAID. Anything less, and you're better off making a separate backup.
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  8. #8
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    Okay, so I'm looking at that Western Digital RAID box and it seems there's only one drive in it. I'll have to do some more googling on it to make sure.


    But the bottomline is if I'm looking at getting a single, safe, backup storage box, it should contain at least three drives, yes?


    If not, just buy two identical boxes, and store data redundantly.

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  9. #9
    Robert Wellock silver trophybronze trophy xhtmlcoder's Avatar
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    If you don't already you might want to consider a Network Attached Storage (NAS) disc. Although I believe they tend to be used for networks with several clients so is probably overkill.

  10. #10
    SitePoint Wizard silver trophy Crazybanana's Avatar
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    after losing some work in the past, I now use 3 different hdd for my backups. but i'm paranoid but it works, and i feel i can relax now.

    I would also add that i had trouble with almost all my WD drives and is now only buying Samsung.. but i did buy a 2TB WD a few weeks ago as that was the only one i could get my hands on the day i needed it. I just hope it works better than the other ones i have tried.
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  11. #11
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    Alright, so I'm thinking of going with a harddrive enclosure and a pair of 2TB harddrives.

    I'm thinking it would be more flexible in future (I could just buy more harddrives as need be), and the total price would come off better than the WD boxes.

    Thanks for the input, everyone!

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    with sixty seconds' worth of distance run.

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