RAID 5 + CallDigit + TR4M

Discussion in 'Mac Pro' started by nickd06, Jan 23, 2009.

  1. nickd06 macrumors member

    Joined:
    Oct 25, 2005
    #1
    As the topic says:

    I want to use the TR4M (4 Bay Enclosure) in a RAID5 set. It comes with a card but I have heard bad things about the card (at least referring to a mac pro). So I thought If I spent the $ I could get a 4 port caldigit and expand at a later date if wanted... the main point being a RAID5 set...


    Any thoughts?
     
  2. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #2
    If you do go with CalDigit, you have to use the HDElement enclosure, as the card won't work with any other enclosure. :( It's intentional BTW. :rolleyes:

    The HDElement also uses Hitachi consumer drives. Total crap, as Hitachi won't support their drive products.

    Personally, I'd look at other options if you want to be able to pick and choose your components. Depending on what you want/need, you might want to take a look at:

    HighPoint
    Areca
    Accusys (ODM for CalDigit, and available at newegg last I looked). Works with other external enclosures.

    Beyond this, I can't help much, as there's too little information to go on.

    Here's some questions to consider, as the answers will help point you in the right direction:
    Drives: Type (SATA/SAS), quantity, including future expansion.
    RAID type (0/1/5/....) [future use as well, as RAID 6 is gaining favor]
    OS environment: OS X only, you might take a really good look at HighPoint. For a multiple OS system, look to Areca, or even Atto (more $$$)
    Do you need boot capability.

    Whatever you do, do not mix internal and external drives into a single array. You're begging for trouble if you do.

    I would recommend using a separate OS drive. It's safer, easier, and actually boots faster than a RAID card, as there's no initialization time.

    Given the abuse presented by RAID, it's definitely in your best interest to use enterprise grade drives, not consumer units. They cost a little more, but are worth the extra reliability they provide. And in some cases, compatibility as well. Particularly if you use a SAS RAID card. (They're really picky with drives). Check the HDD Compatibility Lists for the card/s you're interested in before buying any drives. It can save you dealing with returns later. ;)

    You can also mount additional drives internally in the Mac Pro. Either DIY or using mounting solutions. Maxupgrades has a few that were designed specifically for a Mac Pro. Not exactly cheap, but they do work.

    Another thing to consider is the cabling needed. Not exactly cheap, and needs to be taken into consideration when planning costs. i.e. Mini SAS Fan Out cables are typically $30 each, and attach 4 drives to the card. This is also the same cable needed to attach the logic board to a separate OS drive, since Apple chose to use the Mini SAS connector.

    There's a lot of detail associated with RAID, so be patient. ;) Get your information/answers first, and avoid incompatibility issues. :)

    Hopefully, this can help get you started. :D
     
  3. jasleinstein macrumors newbie

    Joined:
    Nov 18, 2008
    #3
    I went down the Caldigit route, then figured out that to extend beyond the Mac, I had to buy cases and drives from them. not
    I bought one of the Areca cards. Works like a champ with 5 1TB drives in a 4TB raid five, and two 3 1.5TB drives in two 3TB raid five arrays. Now I have the confidence when it comes time to expand the drive arrays, the Areca solution will let me do it.
    Also it seems to be pretty fast. I took out a 1.5TB drive and replaced it, just to make sure I new what to expect. The raid controller rebuilt the drive in five hours, which I consider fast.
    Yes I have the 1.5 Seagate drives. I went thru the pain in the butt, firmware upgrade and they seem fine now.
     
  4. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #4
    I don't get why people recommend not using RAID (greater than Raid 0) for the boot drive.

    RAID is not only about data protection but also about higher availability. Who cares how fast your Mac boots? Are you rebooting it 20 times a day?? If you are setting up a RAID 5 array for a single system, it would not make any sense to have a separate boot drive. If you need a big RAID 5 array, the OS and Apps are not taking up all that much space compared to what is available and the data you are going to store. Including the boot drive in the RAID 5 array will actually make the array faster and allow you to more efficiently utilize the total drive space available.

    Rebuilding a boot drive with OS and apps in a pain in the butt.

    I builder servers for data centers often and I NEVER build one that does not include the boot drive in a RAID array.

    S-

    P.S. I never use RAID 0 arrays.......you are just asking for trouble.
     
  5. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #5
    I prefer to boot off a separate OS drive. No RAID involved. :D

    I agree, RAID 0 = major can of worms that should be left unopened. Permanently. ;)
     
  6. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #6
    What is your logic for doing this?

    S-
     
  7. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #7
    Safety and simplicity. ;)

    If the OS drive dies, it doesn't affect the array (data). Particularly if a situation of simultaneous failures occurs. For example, a drive dies, a new one is put in. The rebuild begins, and another drive dies. (Think RAID 5 on a larger array, and usually they're consumer grade drives). Ughh...

    If the array dies (unrecoverable in particular), the OS is still in tact. I found it much faster and easier to reconstruct/replace the array.

    So I figure a single drive is super cheap insurance to avoid potentially major aggravation. :D
     
  8. Virtuoso macrumors regular

    Joined:
    Feb 21, 2008
    Location:
    Seattle
    #8
    I have the Caldigit card and originally set it up with 4 drives in a bootable RAID5 array. I had so many problems with the system just repeatedly failing to boot (kernel panics galore) that I scrapped that setup and stuck a separate boot drive in the optical bay. I've had no further issues and it all works ok now.

    Sidewinder, I know what you're saying about having your boot drive protected by a RAID5 array - that was my original logic, but if your controller starts playing up then you're really screwed.
     
  9. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #9
    That's not all that logical. The odds of any two drives in array failing within days of each other, much less at the same time, are incredibly low.

    If you build a RAID 5 array with consumer drives, you still have a low chance of any two drives in the array failing with days of each other. I, personally, would never build a RAID 5 array with consumer drives. I would use Nearline Storage drives.

    Regardless, if you are going to build a RAID 5 array, it make no sense not include the OS and applications. The whole idea is redundancy, resiliency, and high availability. I can not think of a good reason to run a separate drive for OS and applications unless there is some space issue or drive limit issue.

    S-
     
  10. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #10
    Sure. But you have to pick a good RAID controller or you are screwed no matter what. If you data is not available it doesn't much matter where your OS and applications are, does it?

    S-
     
  11. UltraNEO* macrumors 601

    UltraNEO*

    Joined:
    Jun 16, 2007
    Location:
    近畿日本
    #11
    Yeah, I've experience some of those issues when I first started out. Learning about RAID was a complicated and expensive task (time wise)... At first I went with the recommended Seagate drives, as suggested on caldigit's site but they kept burning out!! I'm talking three units in the space of three months, I'm curious, perhaps I got a bad batch?

    Six months in to it, i'm still using WDC Black, for video work and it's superior seeks times, they seems to be much more reliable. For a consumer drive they're pretty damn good!!

    Anyway separate boot/system drive is the way forward. I consider my data to be more valuable than the boot drive content, having a slightly slow boot isn't a huge lost.:)
     
  12. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #12
    I understand your point. Statistically speaking, you're correct. But I have seen this with consumer drives (not enterprise), so it's not just theoretical to me anymore. Granted, it was almost certainly a bad batch that had sequential S/N's. But it can actually happen. Unless I know for certain, I assume most are interested in consumer drives, and place a single order.

    Given the nature of the questions on the forum, I've usually had the impression that:
    1. Speed is of more importance than 24/7 availability. (Shutdown/Reboot frequency similar to a typical desktop use).
    2. It's a Mac Pro, so drive space is limited.
    3. Most only go with a 4 or 8 port card.
    I should have been more specific. Sorry about that. :eek:

    No, I wouldn't do this in a high availability server. Large array rack systems I don't expect to be turned off. So using RAID5 (or even 6 on a remote), for the OS and apps is certainly in order in such a system. ;)
     
  13. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #13
    1. My experience shows that most people care about boot time only because it is "cool" to boot quickly. The reality is that people are not rebooting their systems on a regular basis so fast boot speed is not actually important. What is the difference anyway? 60 seconds at most?

    2. Space is limited. But how many people need more than 3TB (RAID 5 using 4 1TB drives) or 4.5TB (RAID 5 using 4 1.5TB drives) of disk space including OS and applications?

    If you need more than that, you are building an external array anyway and you can still boot from that if you buy the right card.

    3. See 2.

    I don't understand your point about consumer drives and failures. You use that point as a justification for not putting the OS and application drive in the RAID 5 array. Yet a multiple drive failure in a RAID 5 array storing only data is just as possible as with a RAID 5 array storing OS, applications, and
    data. So separating out the OS and applications doesn't help. In fact, it hurts reliability and resiliency. Your point about consumer drives should cause you to recommend against using them in a RAID 5 environment in general. Two drive failures in a "data only" RAID 5 array and the contents of the array is gone. Having the OS and applications on the array does not increase the odds of a two drive failure.

    I am amazed that you actually recommend a configuration where the OS and application drive has no redundancy at all. It's not at all logical.

    S-
     
  14. rylin macrumors 6502

    Joined:
    Aug 18, 2006
    #14
    If built correctly, then I agree with you.

    Most people, however, buy disks from the exact same lot, meaning any manufacturing defect will show up in all disks.
    They also never have spares available, and so they might end up with a degraded array for a week or more while waiting for a new disk to show up.

    You also have to keep in mind that rebuilding a RAID-5 volume takes a lot of time, constantly stressing the disks, and that may well push a working drive over the edge.

    While I dislike RAID-5, it's decent enough for home use, but I'd probably consider the R5-like RAID-Z or RAID-Z2 (at the cost of another disk) instead.

    For professional use, I wouldn't touch anything that isn't a nested RAID set.
     
  15. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #15
    Then these people should not be utilizing a RAID 5 array for anything, much less important data files.

    To do RAID Z, you need to be running ZFS. Today that is not really an option for OS X. Nested RAID sets are great if you can afford to buy more than twice as much storage as you actually need. That's usually doable on a small scale, but there aren't many people that are willing to buy 10 drives for 4 drives worth of storage.

    S-
     

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