Dumb Question Re: RAID, SSDs, and Boot Volumes.

Discussion in 'Mac Pro' started by SuperJudge, Jan 12, 2011.

  1. SuperJudge macrumors 6502


    Apr 2, 2008
    The Triangle, NC
    So I'm considering a new boot volume for my Mac Pro revolving around this RAID controller, since I have had great experience with 3ware's products in my Linux boxen and it really seems like $700 for the Mac raid controller is a bit much.

    My workflow revolves very heavily around virtualization. I've been thinking about a variety of options for SSDs and hybrid drives and even just fast laptop HDs. Am I crazy for considering 2.5" drives other than SSDs? I'm thinking of 2.5" drives because I put a pair of them in the lower optical bay without issue.

    The amount of storage needed on the boot volume is probably in the range of 150-200GB. Getting SSDs that size may not be in the budget. Thus, I am currently considering either a pair of 320GB WD Scorpio Blacks or a pair of 250GB Seagate Momentus XTs. I'm not sure the hybrid Momentus drives are worth it. Additionally, I know that a lot of SSDs don't fully support RAID in their firmware. Thus, I am reluctant to buy one, let alone a pair, since a lot of places don't seem to have terribly generous return conditions for SSDs.

    Is this a fool's errand? Should I just relegate my VMs to other storage and get a smaller SSD for the OS + apps?
  2. nanofrog macrumors G4

    May 6, 2008
    First thing's first.

    The 3Ware card will not work in the MP.
    1. It does not contain EFI based firmware, which means it cannot boot OS X.
    2. Even if you only want it for a data array (use a separate boot disk on the ICH), there's no drivers either.

    Another note; the Apple RAID Pro is an expensive pile of junk, so stay away. You can get a card that will work much better, and may be cheaper, depending on your actual needs (including future growth).

    There are mounting solutions from 3rd party companies, such as MaxUpgrades and Trans International (can range from adding disks in the optical bays in both 2.5" and 3.5" varieties to mounts that hang off of an HDD bay).

    So there's more options than you may be aware of. :)

    You don't need to bother with RAID for the boot disk, unless the system needs to be available 24/7. If you do have such a need, then use a RAID 1, as the point is to make sure the OS is still operational in the event of a disk error.

    As per what you're trying to do overall, there's lots of options. But you need to ask yourself some questions:
    • What is your budget?
    • What kind of throughputs do you actually need?
    • Filesizes?
    • How do you use the VM (need specs, such as allocation information, .... - can help if you don't know what your throughput need is)?
    • Does the array need to be redundant?
    • Are you going to run a level that OS X cannot do (OS X can only do 0/1/10 and JBOD)?
    • How many disks?
    • What is your primary data storage capacity requirement?
    • Do you need the card (if required) to boot OS X?
    • Will it be used with more than one OS (natively, not VM)?
    Such answers can allow members to help guide you to a viable solution. ;)

    See above.

    Once answered, we can answer this question. :p
  3. SuperJudge thread starter macrumors 6502


    Apr 2, 2008
    The Triangle, NC
    There's drivers from LSI for the 9650 series of RAID controllers, but the lack of EFI is going to be the hurdle I hadn't considered. Oops!

    Thank you for confirming my suspicions.

    Awesome! :D

    The system in question is my primary workstation. I work in end-user support and system administration. Downtime is a serious inconvenience for me. I recently had a server eat itself following a kernel and it had been running a software RAID 1 unbeknownst to us because we inherited a server someone else had set up. My system is currently also running a software RAID 1, thus I am a bit paranoid that the system is going to lose power or kernel panic in the middle of a read/write operation. This might be an unfounded fear, but there you have it. Additionally, being able to off load the RAID operations from the main CPU would be great.

    • What is your budget? $500-600US
    • What kind of throughputs do you actually need? Not entirely sure. Something a bit better than I have now?
    • Filesizes? The VMs are single files in the 20-40GB range.
    • How do you use the VM (need specs, such as allocation information, .... - can help if you don't know what your throughput need is)? In conjunction with Fusion, I've got one Windows VM set up to run in Unity to provide me with the Windows apps I need. A second Windows VM is used for Active Directory tasks and as a target for RDC sessions. A pair of Linux VMs used for a variety of purposes rounds out the mix.
    • Does the array need to be redundant? Redundancy is preferable.
    • Are you going to run a level that OS X cannot do (OS X can only do 0/1/10 and JBOD)? RAID 1 is my target, but being able to do 5 or 6 wouldn't be bad.
    • How many disks? 2 to 4.
    • What is your primary data storage capacity requirement? Storage to cover all the VMs and such? About 120GB. Storage beyond that is being handled by other disks and is in the 600GB range. I'm not sure that most of that data would need to be terribly high-speed.
    • Do you need the card (if required) to boot OS X?Yes. This would certainly be preferable.
    • Will it be used with more than one OS (natively, not VM)? No. Only Mac OS X gets booted on this machine.
    If it helps, this is a Mac Pro 1,1 with dual dual-core 3.0GHz procs

    Thanks for guiding my question, nanofrog. I was hoping that you'd respond!
  4. cutterman macrumors regular

    Apr 27, 2010
    If reliability is your primary concern I dont think laptop-grade 2.5 mechanical drives are the way to go.

    A compatible RAID card (Areca or Atto) and a couple of 2.5 SAS drives would offer good performance and excellent reliability if you want to stay away from SSD's.
  5. nanofrog macrumors G4

    May 6, 2008
    I hadn't checked LSI's Support section recently as they went so long without OS X drivers. I'd the impression they were never going to be created it took so long. I was actually thinking you were going to try and use the BSD versions in (possibly in some hack).

    Good to know they finally released drivers.

    OK. A couple of simple questions as to what your overall storage goals/needs are.
    • Are you just looking to RAID the OS/applications location?
    • What do you have/need for your primary working data (single disk, RAID, ...)?
    • What do you have for a backup solution?
    As per your fears of a lost write, keep in mind that an OS/applications disk is almost exclusively read only (put your working data on another location). Now for working data (write locations), you need to run a Line Interactive UPS that uses a Pure Sine wave inverter design (Refurbished units can be had for about the same money as stepped inverter models, which do not do well with active PFC based PSU's).

    I'm trying to get a feel for what you have, what you may yet need, and if it will fit within the budget listed below (not sure it will, assuming the working data location needs to be tweaked).

    For a RAID 1, it's only going to "cost" you ~1% on a single core, so it's best to use OS X and the system resources to operate it (definitely cheaper, as a decent RAID card is still going to be ~$300USD - half of your budget, and you've not bought a single disk yet). BTW, with such a card, you'd need to run enterprise grade disks in RAID for stability reasons (the recovery timings are critical, as the card takes over the functions from the OS, and it's not done the same way).

    If you're not running operations at night (need for 24/7 operation), you could just run a single disk for the OS/applications disk and keep another disk on hand for a clone (internal or external). I'm just not sure if you're running 24/7, or will be able to spare the 20 min or so it would take to restore a broken OS/applications disk (assuming you restore from the clone, not just swap it, which is even faster). As per size of the OS/applications disk, most can do with less than 60GB if you really need to use an SSD (it is the fastest tech for random access, but it's also a bit on the pricey side in terms of cost/GB). But if you can suffice with say 40GB, OWC has that size for $100USD last I checked.

    Budget: Not absolutely sure yet, but I'm thinking it's too low (presuming you need a good UPS and everything else right now - nothing much on hand that can carry over and save on costs), depending on how you answer the questions.

    Throughputs: Do you only need this for the OS/applications disk?

    RAID level: 5/6/50/60,... will definitely require a card, and that will eat your budget almost entirely on it's own. You'd be lucky to get a disk to go with it. :eek: So depending on how you answer the above questions, the best way to go is likely an SSD for the OS/applications disk (single, not RAID), and a small, inexpensive mechanical to make clones on for recovery purposes if you've ever a problem (corruption, bad disk,...).

    Past this, I'll wait for your response, and see where to go from there, as your budget is a significant limiting factor right now (if you're already running a good UPS, this will help, and if a single disk will be sufficient for your working data requirements, that will as well - just need a single disk to back it up).

    If it's reliability rather than speed that's needed, enterprise grade 2.5" disks would be better, and required if it's run on a hardware RAID card such as an Areca. But if the RAID 1 is meant solely for an OS/applications disk, SSD's are good for read reliability (no moving parts, and it doesn't wear the cells). It's writes that mechanical is better suited to than MLC based SSD's (even the newer forms, such as eMLC from Micron).

    Areca would be the most cost effective for a card, with ATTO coming in second (sadly, they're more expensive than Areca, nor do they include any internal cables either).
  6. SuperJudge thread starter macrumors 6502


    Apr 2, 2008
    The Triangle, NC
    --Probably, but having at least one of the VMs on this volume is desirable.
    --Working data is also in a software RAID1, but backed up on a server regularly, and more trivial to restore.
    --I'm using Time Machine for odds and ends and immediate recoveries of "oopsies!" moments, monthly Carbon Copy Cloner sessions for a bootable backup, and CrashPlan for disaster recovery

    After reading this, I'm really not sure that a RAID card will be necessary. I do have a rather nice APC UPS unit, but now I'm going to have to see if it's line interactive pure sine wave or not.

    Not running 24/7. This might actually be the best option. Thanks for confirming that I was leaning towards unnecessary paranoia on a lot of fronts. I think I had a solution in search of a problem that was different from the one that I have.

    Thanks for all your help!
  7. nanofrog macrumors G4

    May 6, 2008
    So you're just running a single location for OS/applications and working data (mention of OS array caused me some confusion as I had the impression it was separated from the working data).

    If you want redundancy, RAID 1 is the cheapest way to go (n = 1 failover). You can do n = 2 on the cheap by using 10 if you wish (implement it via OS X's Disk Utility), but it will double the disk cost. You also get double the speed for sequential access however, so it's not just redundancy. :) Unfortunately, this doesn't apply to random access, which it seems you're more interested in (load the VM's faster). But that's really going to be the initial launch anyway. For this, I'd still go with SSD for OS/applications.

    Your backup is acceptable for what you're currently using, and if it's not going to change (single location for everything), then it will continue to work (it would work with 10 as well, so long as you've sufficient capacity with the backup system).

    IF you want it all so to speak, then split the OS/applications from the working data using an SSD. Keep a clone of the OS in case of a failure, and make a RAID 1 or 10 (10 if your working data requires sequential access rather than random). Then use your existing backup system for the 1 or 10 (whatever you decide).

    Not terribly expensive either, and doable within your budget. Nor are you required to run enterprise grade disks as you would be with a proper RAID card. Though it's still a good idea, as they're more rugged and worth the additional expense IMO (you can use the WDTLER utility to change the recovery timings in the drive firmware to 0,0 if needed <what consumer disks are set at>).

    Search the P/N, and read the specs carefully (specifically the inverter section).

    :cool: NP. :)

    You've another option or two, depending on what you need (see above). ;)

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