Mix HDD capacities in Raid 5 Array

Discussion in 'Mac Pro' started by Renderz, Feb 3, 2011.

  1. Renderz macrumors 6502

    Feb 27, 2004
    Hi guys,

    First, let me apologies as this isn't directly an Apple question but I couldn't think of anywhere better to get a quick answer.

    I have a RocketRaid 2320 Raid card inside a Windows 7 machine. The card has 8 ports, 4 of these ports currently have 1TB HDD attached in a Raid 5 Array. Could I add 4 more 2TB drives to that Raid 5 array? There doesn't seem to be a clear answer if I can mix and match HDD with different sizes.

    Many thanks.
  2. philipma1957 macrumors 603


    Apr 13, 2010
    Howell, New Jersey
  3. nanofrog macrumors G4

    May 6, 2008
    Generally speaking, Yes, you can mix different sizes and makes of drives (there are the occasional exceptions with inexpensive products). The usable capacity however, will be based on that of the smallest disk in the set. So:
    Usable capacity for RAID 5 = (n - 1) * capacity of the smallest disk​

    So in your case, those 2TB disks will still be treated as 1TB disks (usable capacity = 7TB). The other 1TB per will go unused. You can partition them off to gain access to it, but you wouldn't want to use them simultaneously with the RAID 5.

    Unfortunately, I recall reports that the Online Expansion and/or Migration features on this card are problematic (Highpoint's not a good company to buy RAID products from, as the support sucks, and the products are inconsistent - some work well, others barely, if at all). It also causes the disks to be unusable with other disk controllers.

    So if you're looking to upgrade, you should seriously consider getting rid of it, as you'll be better off in the end. Seriously. Take a look at that card's (and company's) reputation. It's not good. :eek: :(
  4. Renderz thread starter macrumors 6502

    Feb 27, 2004
    Thanks for that info NanoFrog. I looks like I'll need to wait until I can get at least 3x 2TB drives, install it as another Raid5 array on the other SATA Ports then transfer the data from the Old array to the new one.

    As for your concerns with RocketRaid I am well aware their support is poor, but in the many years of IT I've not seen any company that does have perfect support. I got it for a low price. My Windows 7 machine is my secondary backup solution (my primary is a Synology DS1010+) so if it goes wrong i won't have lost all my data.

    Thanks again.
  5. nanofrog macrumors G4

    May 6, 2008
    So long as you've the ports, its the best way to go about it. No matter if you keep the card and use it exclusively, swap it out, or run another card as well (i.e. move to a different brand for your primary, and use the RR2320 for your backup solution).

    Granted, any of them can end up with a bad support response (every once in a while, and can usually be gotten around by getting in touch with another support person). Unfortunately support wise, Highpoint is consistently horrible. If you don't or won't ever need help (don't need firmware, and hope the drivers will suffice once no longer updated, as they don't support products for long), and really know what you're doing, then using their products is a possibility (so long as the card actually works). Unfortunately, their products don't work consistently in my experience (all of it is ODM'ed by multiple suppliers).

    Please understand, I've had a few too many bad experiences with their products (personal and professional use), so they've left a really bad taste in my mouth proverbially speaking. So I don't want others to make a mistake by using the wrong gear.

    For whatever it's worth, I hope this helps. :)
  6. Renderz thread starter macrumors 6502

    Feb 27, 2004
    I do appreciate your concerns. I would probably would not invest in a RAID card at all if I didn't have my Synology NAS; I always prefer some sort of NAS or DAS device. In the past I've had a Drobo which worked flawlessly.
  7. nanofrog macrumors G4

    May 6, 2008
    A single disk attached to the ICH qualifies as DAS (D = Direct afterall ... ;)), but the term is usually applied to like running a proper RAID configuration that's running directly on the system.

    I use proper RAID cards to give me both redundancy, speed, and a balance of both in terms of cost (i.e. RAID 5 or 6), as 10 tends to be too expensive for my requirements. Nor do I care for software implementations, even for levels that Disk Utility are capable of (I do recognize when they're viable, but there's other issues besides costs to deal with for some applications).

    For a backup, I tend to use ZFS based arrays in tight budget situations where a PM enclosure won't work (also makes for a good DIY NAS when on a dedicated system). It can be done on a SAN as well (gets more complicated though, due to failover and/or networking throughput requirements).

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