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Mac Pro RAID?

post #1 of 12
Thread Starter 
Hi everyone,

I've heard that the Mac Pro doesn't have hardware RAID. If I were to use software RAID, would that mean that the array of disks was only visible by OSX?

Thanks,

David
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post #2 of 12
Quote:
Originally Posted by iMacfan

Hi everyone, I've heard that the Mac Pro doesn't have hardware RAID. If I were to use software RAID, would that mean that the array of disks was only visible by OSX?

While I don't have an answer for you... Barefeets had reported something very interesting about the RAID support WRT the Pro Macs. Aside from the 'speed issues' they found when using 4 750 GB drives that everyone seems to be focusing on another thing they stated was that the Mac Pro could BOOT directly from a RAID they created.

Unless I'm mistaken this is a 'first' isn't it? Most/all Macs in the past couldn't do that with a normal (not 3rd party cards) RAID setup. So, is this an indication that the RAID in the Pro's is in fact a 'Hardware RAID' or just that they somehow wrote the Pro Mac firmware to recognize and boot from the 'Software RAID'.

Edit:

Linky: http://www.barefeats.com/quad07.html (see mid/bottom page Q&A area "Can I boot from an internal RAID 0 set on the Mac Pro?")

Edit2:

gwoodpecker (below) confirmed that G5's can/do boot from internal (built in) RAID-0 and RAID-1 so this is NOT something 'new' for the Mac Pro.

Dave
Apple Fanboy: Anyone who started liking Apple before I did!
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post #3 of 12
First of all, every PowerMac G5 with two SATA harddrives of identical size could be configured as a software RAID (0 or 1) before installing OS X by using Disk Utility on the system DVD. You were able to boot OS X from both RAID 1 or 0 (which is what I still do).

Secondly, creating a RAID in normal OS X allows only RAID 0 and 1. So with the Mac Pro, you could have one startup disk, a two-disk RAID and still have one drive bay free. Or you create a three- or four-drive RAID-0 (where data integrity is pretty much = 0 when one drive fails...). With OS X Server, if I recall things correctly, you can also create RAID-5 volumes. With four drives in the MacPro, a RAID-5 would generate 3x the size of one of the disks (e.g. 1.5 TB when using four 500 GB disks), with good data integrity (due to the parity information being spread across all drives) and quite good write and read speed.

Concerning the formatting: volumes formatted with HFS+ are only visible in OS X and not in Windows (unless you're using some super-duper special software for Windows). If you create a FAT32 formatted disk, both OS X and Windows can see (read AND write) to it. When using NTFS as formatting option in Windows, OS X can only see (read) the files but you can't write to that disk.

And it's even more complicated: FAT32 volumes can only be 32 GB in size when formatting them in Windows, so a RAID configuration is pretty much out of question anyway because of the small size. (P.S. When using Disk Utility, I found out a few months ago that you can format external harddrives with FAT32 regardless of its size - I used a 2.5" 60 GB LaCie mobile drive - , Windows XP can use it just like that).

Hardware RAID means: a special controller chipset takes care of striping or mirroring the data onto several harddrives, whereas with software RAID, the regular CPU(s) take care of it. With RAID-5, a lot of parity information must be written, therefore making software RAIDs a lot slower than using a dedicated hardware RAID-5 card.
post #4 of 12
I'm thinking of RAID 0 on two seagate 250 GB .10 for the startup disk and using the 250 GB .9 that comes with the system for backup (also to an external firewire disk)....... but open to suggestion/benchmarks..... this Mac Pro is unlikely to have Windows installed but may add Solaris (the Mac Pro should arrive today-tomorrow).... quick tutorial on RAID at http://www.acnc.com/04_01_00.html
post #5 of 12
Thread Starter 
So I can't use RAID-5, then? I was hoping to use three 250-300Gb drives to make a 500-600 volume, for not too much money.

David
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post #6 of 12
Quote:
Originally Posted by iMacfan

So I can't use RAID-5, then? I was hoping to use three 250-300Gb drives to make a 500-600 volume, for not too much money.

David

Without OS X Server, nope, you get only multi-volume RAID-0 or two-/four-disk RAID-1.
post #7 of 12
Quote:
Originally Posted by gwoodpecker

...You were able to boot OS X from both RAID 1 or 0. (on a G5)

Thanks for the confirmation (on G5's being able to boot from internal RAID) gwoodpecker not to mention the rest of the information, very helpful indeed.

Dave
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post #8 of 12
Is software RAID-0 as fast as hardware (or nearly?) Will I see a performance benefit from 2 RAID-0'd 160GB HDDs versus a 250 GB HDD, assuming all are 8-16MB cache and 7200rpm? Because I read somewhere that the harddrive could be a potential Mac Pro bottleneck (along with RAM latency)
post #9 of 12
Quote:
Originally Posted by ZachPruckowski

Is software RAID-0 as fast as hardware (or nearly?) Will I see a performance benefit from 2 RAID-0'd 160GB HDDs versus a 250 GB HDD, assuming all are 8-16MB cache and 7200rpm? Because I read somewhere that the harddrive could be a potential Mac Pro bottleneck (along with RAM latency)

In my G5 DualCore 2.0 GHz, I have a RAID-0 with two (not even identical) 7200rpm SATA drives (8 MB of cache each). Read and write speed for the RAID-0 is about 100 Megabytes per second (measured with Helios LAN Test 3.1 on the local harddrive -- which gives quite accurate results when using 300 MB test files, saturating both the two SATA buses and all drive caches). One single, not RAID-ed drive goes up to about 60 MB/sec, depending on the drive.

Modern SATA-II buses have a theoretical bandwidth of 3.0 Gbit/s (around 300 MB/sec effective speed) and most 7200rpm harddrives today use up only about one fifth of that bandwidth. So harddrives can indeed be some kind of bottleneck. Using 10K or 15K drives is better and faster, but they run louder and a lot hotter. You might get over 80 MB/sec per drive using those.

Hardware RAID is always faster because of the deditated processing units. Maybe in RAID-0 configurations, the speed difference is not so big, but when using RAID-5 where a lot of parity information needs to be computed, the difference is huge! Servers almost always use hardware RAIDs for that reason.

One single 250 GB drive, however, is for sure a lot slower than the two-drive 160 GB RAID-0.
post #10 of 12
Quote:
Originally Posted by gwoodpecker View Post

Without OS X Server, nope, you get only multi-volume RAID-0 or two-/four-disk RAID-1.


OSX Server will not allow software raid 5. I tried and it is the same as standard osx raid 0 and 1
post #11 of 12
Welcome to the forums. But why did you dig out a thread this old? \
post #12 of 12
Sorry to resurrect this thread again but it's the closest I've found to my particular issue;

I have a new Mac Pro (early 2008) and had it delivered with Mac OSX (Leopard) on the drive in Bay 1 and a second drive in Bay 2 upon which I've since installed Windows XP x64 (SP 2c). So far, so good and every thing seems to be working.

What I am now trying to do is to install my two WD Raptors from my old PC into the Mac Pro for storing my data on. I'd like to set them up as a RAID 1 (mirrored) so that they are automatically backed up. They are not going to be used as boot disks, purely for data storage that I can read & write to from both OSes.

If I create a RAID 1 in OSX with Disk Utility, it cannot be seen in Windows XP x64 (drives are noted as 'unspecified?' partition with an 128MB EFI partiton at the front of the drives). In Windows XP Disk Management I can't convert the disks to dynamic and so can't set up the mirror there either.

If I create two separate FAT32 drives in OSX they work fine in both OSes but that rather defeats the object of setting up the RAID mirror.

Does anyone have any helpful advice on how to (or whether I can) set up a RAID 1 mirror that is readable from both OSes?

(I did find a product called CrossStripe - http://www.mediafour.com/products/crossstripe/ - but this won't work with Windows XP x64!)

TIA,
oz.

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oz.

"Make lunch, not war."

Visit - www.RichardOsborn.com
for all things 3D, especially XSI.
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