Everything you ever wanted to know about Software RAID, but were afraid to ask!

[dgdosen]

Under ideal conditions RAID 01 will give higher reads, here's why:

You've got two striped arrays that are being mirrored. Under a true RAID 1 mirror, read speeds are increased, because it can stripe the reads from all the mirrored drives. So, in the case of RAID 01 read speeds could be increased. I know, I know, you're thinking, "Wait! RAID 10 has mirrors as well, it's just backwards, but you should still get a read speed boost!" The short answer, is no. When the mirrors are on the other end, the overheard is to high to see a boost. (At least that's my understanding of why it didn't work in 10... It seems a little fishy to me, I'll research it a bit more and update accordingly.)

This has been my experience with a 3ware card that supports 01 and 10, at least.

Have you repeated this test at all on 10.5? I'd like to see if RAID 01 is performing better, or if it would be the better choice compare to RAID 10...

 

[dgdosen]

One thing I should mention, you cannot setup RAID 01 or RAID 10 via Disk Utility on the Mac Pro Installation Disc. It just doesn't work. I talked to a friend at Apple and he checked and confirmed that it is a known bug. It's a issues with the pasteboard they use on the CD, not allowing drag and drop to work properly (which is required for multi-array RAID setups). What you'll need to do is install 10.4 to a firewire drive, boot from that, setup your array that way then do a normal install.

Still an issue? My Mac Pro arrives in a couple of days and I'd like to avoid the extra step of installing to another device...

Although it might be interesting to stick an install on an iPod and connect it via firewire. I may need to try that...

 

[thedommer]

is there a huge difference between using 32 k or 256k? I set mine up at 128 then changed something and didnt realize that it defaulted back to 32 k until after I had trasferred all my data on the raid. I really dont feel like moving 1TB of data off just so I can reformat my raid at 128 instead of 32. I do alot of photoshop work, audio and video.

 

[jb60606]

will video encoding benefit from a striped array?

 

[WardC]

My Mac Pro is on order (Refurb Quad 3.0GHz) and now I am looking at purchasing RAM and disks to install in the machine once it arrives. A variety of possible configurations have appealed to be, and I am even considering a 2-disk RAID 0. I am looking at that WD 150GB Raptor (10,000rpm) but, for the space it provides, it's a pricey disk (About $209 from OWC)...so a 2-disk 300GB RAID 0 system with those would be about $420.00.

I don't really rely on my Mac for video editing, although I do it from time to time, mostly with iMovie, and I have dabbled in FinalCut. I run Bryce alot and do 3-D editing, and basic Photoshop stuff, but nothing that would really demand a tremendous amount of hyper-disk speed. I download alot of files, music, and video, but my maximum download speed is usually around 550k/sec, and really wouldn't require anything super-ordinary as far as disk speed.

So, right now...I am looking at maybe getting one Raptor 150GB drive and using this as a boot disk, with my system and my Applications...then getting a couple of 500GB Seagate drives with 32MB cache, and using one for media storage, and the other partitioned to use for a Windows XP disk. Then I will just keep the other stock 250GB as a backup drive, or a secondary boot drive. I think this should work fine, these are all fast drives, relatively, and my needs really don't call for a RAID system, or now at least. I could always configure those 500GB drives into a RAID 0 system at a later time if I needed the speed.

-Ward

 

[AviationFan]

will video encoding benefit from a striped array?

Oh yes! The moment you do more than editing single streams of DV or HDV, you'll benefit from (or need) the additional bandwidth that comes from a striped array: multiple streams for multi-cam editing, uncompressed video or higher bitrate codecs. The other nice thing about video editing and hard drives is that backups are often not that important - the original footage is still on tape (assuming you archive your tapes, instead of reuse them), and render files can always be regenerated. In other words, you can afford to keep capture and render files on a striped array with a higher probability of data loss. Just store your other, smaller project files on a drive with higher reliability.

- Martin

 

[jb60606]

good to know, because the drives that will eventually make up my RAID array just arrived. Thanks.

Though, I still can't decide between RAID 0+1 or 10 (w/4x 500GB 16MB SATA2 drives).

This website says 0+1 is better for imaging apps and general file servers, while RAID10 is better for a high performance database server. The OP's benchmarks showed little-to-no difference between the two, so I'm wondering if either has any pros/cons that may separate it from the other. Any recommendations?

 

[AviationFan]

Though, I still can't decide between RAID 0+1 or 10 (w/4x 500GB 16MB SATA2 drives).

If it's just video (as per your previous message), why not make it a simple striped RAID 0 and use the full capacity of the drives? That is, for the render and capture files at least...

- Martin

 

[jb60606]

If it's just video (as per your previous message), why not make it a simple striped RAID 0 and use the full capacity of the drives? That is, for the render and capture files at least...

- Martin

what the hell, you're right. I'll just go with Raid0. With Time Machine, I suppose I don't have that much to lose, aside from time & a little cash (though I'll already have one extra drive), unless the worst happens (I lose a drive and the drive in my TM). Though, just in case, I think I'm going to invest in a raid1 external drive for TM. Perhaps something like the Drobo.

 

[joaoferro99]

Oh yes! The moment you do more than editing single streams of DV or HDV, you'll benefit from (or need) the additional bandwidth that comes from a striped array: multiple streams for multi-cam editing, uncompressed video or higher bitrate codecs. The other nice thing about video editing and hard drives is that backups are often not that important - the original footage is still on tape (assuming you archive your tapes, instead of reuse them), and render files can always be regenerated. In other words, you can afford to keep capture and render files on a striped array with a higher probability of data loss. Just store your other, smaller project files on a drive with higher reliability.

- Martin

What about RAID 5 instead of RAID 0. I am thinking getting a RAID 5 instead of RAID 0

 

[brand]

What about RAID 5 instead of RAID 0. I am thinking getting a RAID 5 instead of RAID 0

This thread is about software RAID 0 or 1. Software RAID 5 is not currently possible with OS X in its current state. To achieve RAID 5 you will have to use a hardware controller.

 

[jb60606]

I re-read the thread, and I noticed a user said RAI 0+1 and RAID10 can't be setup via the disc utility on the installation disc. So how did the OP set either up for this test?

Thanks

 

[dgdosen]

I re-read the thread, and I noticed a user said RAI 0+1 and RAID10 can't be setup via the disc utility on the installation disc. So how did the OP set either up for this test?

Thanks

I think that might have changed - but regardless, I took out the stock drive from Apple, replaced with four drives to run RAID 01 - the set them up based on the documentation found in Disk Utility. I created two sets of RAID 0 drives, then used those sets to create a mirrored set. Since this is done in disk utility, you should be able to do it without booting from some other drive.

I haven't done any benchmarking, but they're pretty quick - then can load a VM in seconds - hell, they'll install an OS on a VM in minutes...

I don't however, run bootcamp on my Mac Pro - I do on my MBP. I can't see much of a drawback, except for things like games..

 

[MrGando]

Hi guys, how are your RAIDS working ? I did a RAID 10 ( two mirrored sets and then a striped set ), on my mac Pro , 4 750 GB WD disks. I have been experiencing a lot of kernel panics on my computer lately, and some people in the apple discussion forums told me it could be that. ( I do HD video editing on FinalCut Pro ) .

What do you guys think ?

Here's a link to the apple discussion:

http://discussions.apple.com/thread.jspa?messageID=7358741#7358741

Any help will be really appreciated .

 

[exabrial]

Interesting... What stripe sizes did you use? My numbers beat yours for the most part see attachment. I have the 2008 8x2.8GHZ mac pro. Attached is my benchmark and a screencap of the drives from Sysinfo, they are some cheapie WD's.

I did the same testing you did, but I quickly decided RAID0 was also... just to f*ckin incredible to pass up with a machine like this. I settled on using the smallest possible stripe size, it *really* sped up my small file size writes, but I lost some in the topend.

 

[dgdosen]

Hi guys, how are your RAIDS working ? I did a RAID 10 ( two mirrored sets and then a striped set ), on my mac Pro , 4 750 GB WD disks. I have been experiencing a lot of kernel panics on my computer lately, and some people in the apple discussion forums told me it could be that. ( I do HD video editing on FinalCut Pro ) .

What do you guys think ?

Here's a link to the apple discussion:

http://discussions.apple.com/thread.jspa?messageID=7358741#7358741

Any help will be really appreciated .

I too was having kernel panics - but I think it was from an addition of 4GB of Ram I put in the box from OWC (went from 10 - 14) - I've since took the RAM out, and haven't had an issue.

Need to RMA and get that Ram replaced...