Early '08 internal RAID0 setup question

Discussion in 'Mac Pro' started by 4God, May 9, 2011.

  1. 4God macrumors 68020

    4God

    Joined:
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    #1
    What would be faster for a 3TB software RAID0 setup?

    2 x 1.5TB drives or 3 x 1TB drives? Would it make a difference?

    I'll be using it as a 3TB scratch drive for Final Cut. Lots of ProRes files, you know how that goes...
     
  2. 4God thread starter macrumors 68020

    4God

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  3. spidey3 macrumors regular

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    #3
    Assuming the access speeds for the disks are equal then 3 x 1TB would be faster -- splitting your writes 3 ways instead of 2...

    Spidey!!!
     
  4. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #4
    To answer your question, 3x 1TB disks would be faster.

    Performance of a Striped set = n disks * performance of a single disk (assumes all are the same). So the additional parallelism of drives results in improved throughputs.

    But before you embark on this, think about the following:
    1. Are you a professional earning a living with this machine, or a hobbyist/enthusiast user?
    2. How much capacity do you need now, and what is your growth over the next few years (say 3)?
    3. What is your budget?
    4. What kind of backup system do you have, and is it sufficient to handle the new configuration?
    The reasoning behind this, is if you're a professional downtime is something you need seriously consider. When a stripe set goes, ALL DATA IS GONE. Period.

    What this means is, in the event of a failure, you have to fix it, then restore the data off of backup location/s. So you stuff in a replacement drive, restore the data off of the backup, then have to re-perform the work that was lost between the last backup and actual failure. This gobbles up time.

    Now this is always important, but with a stripe set, the risk of failure is higher than that of a single disk (n * to be precise), so the more members you have, the riskier it is.

    This is fine for a hobbyist/enthusiast user, as they generally have the time on their hands, and little in the way of funds = acceptable compromise.

    Professionals OTOH, don't, so a redundant level is called for in order to reduce this (drive dies, the data remains, and you stuff in a new disk and it automatically rebuilds the data to the new drive). Once done, the performance is back to where it should be.

    Now please understand, that no matter what sort of storage configuration you have, there is nothing that warrants running without a backup system in place. Not RAID of any level or a single disk. So make sure you have a backup, as things can and do go wrong, no matter what you have configured for the primary storage pool.

    BTW, there's another couple of things you can do to speed up your system in terms of storage.
    1. Place the OS and applications on an SSD.
    2. Use a separate, small SSD for scratch space/cache (i.e. 40GB unit from OWC that sells for $100USD).

    If you would, get back to me on the questions, and whether or not you're a professional, and I'll help you from there.
     
  5. 4God thread starter macrumors 68020

    4God

    Joined:
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    #5
    Great info, thanks for that!

    Here goes...

    I'm running an early '08 eight core 2.8 Mac Pro.
    I do a lot of non-profit work and some light entertainment industry work as well.

    Until recently, my wife and I shared this computer so I setup a 128Gig SSD as
    my OS/Apps drive and setup a 3 disk RAID0 (3x1TB) Home folder drive. Then a 2x1.5TB RAID0 Scratch drive.
    All six drives are internal with some mods. Wouldn't mind taking out the two under the optical drive and
    hopefully create some better ventilation.

    Now she has her own iMac. I'll probably still do the SSD drive as my OS/Apps
    but then thought about the other drives and wondered what the best solution would be.
    Maybe just use one of my 1TB drives as a home folder drive and maybe use
    one of the 1.5TB drives as a scratch and the other for Time Machine and don't
    even do a RAID0 setup. Then I could use the other two drives as externals to
    transfer info to other studios. Any further ideas or input would be greatly appreciated. Thanks again.
     
  6. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #6
    I'm still a little lost as to the importance of the data, but am getting the impression that you can't afford to lose it (i.e. non-profit may or may not be paid, and even if it's not paid work, you still answer to someone, and would be expected to be the archival location). As per the light entertainment, this lends me to think this part is paid work.

    Some clarification would be nice (trying to determine the right balance of speed and reliability). BTW, the capacity information requested, including the growth rate, is to determine what the best array level, assuming RAID is actually warranted.

    1. The SSD is fine.
    2. Ventilation should be fine, as the MP's are sectioned off by baffles (assuming your PSU temps are fine; if not, let me know).
    3. Don't see a backup solution here at all (NOT GOOD).
    This could work (at least there's a provision for a backup system with this). But it will also run slower than what you have now, so you must be aware of that.

    Now if you've enough time, and aren't pursuing paid work, this could suffice. But if you are earning a living (even part time), additional speed allows you to get work done faster, and ideally squeeze in more work in the same amount of time (does depend on you being able to actually wrangle the work to begin with ;) = "hard part" to my way of thinking, as it's less stressful and easier to just do the work once you have it).

    Hence the need for clarification. :)
     
  7. 4God thread starter macrumors 68020

    4God

    Joined:
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    #7
    Sorry, yes some is paid industry work and most is unpaid non-profit work.
    I don't rely on it for making a living, I have other income for that but it is still
    important to do the job well and within a reasonable amount of time.

    Speed is important since I'm editing ProRes files but I'm now thinking that
    a backup solution is more important. I could leave the drives where they are
    now (which is SSD in slot 1, 1Tb drives in slots 2, 3 and 4, and 2 1.5Tb drives
    under the optical drive). I'm not sure what the best use of the drives I have and
    how to reconfigure my setup. I just have to figure out the best way to balance
    speed and backup. Anymore input would be great. Thanks again for your help, it's much appreciated.
     
  8. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #8
    If the disks are to be controlled by OS X and the system's hardware, their physical location doesn't matter (all 6x SATA ports are physically located on the ICH and accessible/controlled by OS X).

    In terms of an inexpensive backup, you could look into using an eSATA card + Port Multiplier enclosure (example 4 bay kit; just add drives). There are larger units as well if you'll need to use more capacity. BTW, consumer grade Green drives are good for backup purposes so long as they're not on a RAID controller (cheap too). As per how to configure these, you could do a JBOD (concatenation = adds all the disks' capacity together, and is seen as a single disk to the system; reliability = that of a single disk).

    Now in terms of a primary storage pool, I'd recommend going with a redundant array. Now OS X is only good for 0/1/10 and JBOD, and of those, 1 and 10 are redundant. But only 10 also offers additional speed. Usable capacity is 1/2 of the total capacity (based on the smallest capacity if they're not all the same). So if you've a mix of 1 and 1.5TB disks, it will be based on 1TB (total capacity would be seen as 4TB, usable capacity is 2TB). Redundancy of n = 2 for level 10 (in short, 2 disks can fail without losing your data).

    Past this, and you'll need to run a RAID card (recommend 3rd party, not Apple's card = crap), as they can do levels OS X cannot (i.e. 5/6/50/60, of which 5 would be the most useful for a balance of speed and redundancy for a system you'll have access to in the event a failure does occur). One thing to note, that with using such a card, you'll need enterprise grade HDD's in order for it to be stable (has to do with the timings in the firmware, as control of the disks is under the card, not OS X and the ICH in the system). This is absolutely critical, and such disks aren't as cheap as consumer grade disks. Now this is where capacity and growth are critical, so you need to put some thought into this.

    I'd recommend taking a look at RAID threads here in MR (I've posted a lot on this), as well as the RAID wiki (pay particular attention to the levels).
     
  9. 4God thread starter macrumors 68020

    4God

    Joined:
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    #9
    Thanks again.
    There's no budget for adding a eSata card (or drives for that matter), I just
    had to replace my graphics card. Based on your info and the RAID Wiki, I think
    I might just keep the SSD as is (format and reinstall the OS/Apps), use the 1 Tb drive
    in slot 2 as my Home folder drive, use the two 1Tb drives in slots 3 & 4 as a
    RAID0 Scratch (2Tb scratch drive), then use the two 1.5Tb drives under the optical
    drive as a RAID0 Time Machine backup for the Home and Scratch drives.
    Then I would have 3Tbs of backup for 3Tbs of data (not including the SSD).

    Your thoughts?
     
  10. sammyman macrumors 6502a

    Joined:
    Mar 21, 2005
    #10
    This is pretty similar to what I plan on doing as well. I have been scratching my head though wondering if I should just move the TM backup to an external source. I just want the ability to expand as needed in the future.
     
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #11
    • SSD = OS + applications (fastest for random access, which is what this requires)
    • HDD 1 : 1TB = Primary Data (Home Folder)
    • HDD 2 & 3 : 1TB each = Stripe set for scratch @2TB usable capacity (this is fine, as it's temporary data).
    • HDD 4 & 5: 1.5TB each = Backup data, but do not use a stripe set. Use JBOD instead = concatenation (at least if the primary is gone, and one of the disks in the backup dies, one of the disks can still be recovered via software).
    Given you're not able to currently add anything to your current equipment, the above would be the most viable implementation IMO (not a fan of stripe sets for backups - they're more trouble than they're worth, as I'm accustomed to home users not replacing disks until they die).

    The best way to do this on a budget is to use an eSATA card + Port Multiplier enclosure (easy to expand, and you won't have a bunch of single disks cluttering the workspace).
     

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