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Old Nov 10, 2012, 04:51 AM   #1
scottrichardson
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RAID 0 (4 x SSD) MAX Speed?

Hi all,

If I install FOUR SSDs in my Mac Pro and configure them in RAID, what's the theoretical max throughput I could expect?

I understand the 300MB/sec limit of SATA-II - so does that mean 4 disks will each theoretically have 300MB/sec, with a combined theoretical total of 1200MB/sec?

I'm considering installing an OWC Accelsior 240GB PCI SSD Card as my boot drive, then running 4 x 120GB SATA-II SSD's as my main projects/work volume raided together.

Anyone else done a 4-way SSD RAID 0 internally here?

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It appears I should have searched first, looks like 650MB/sec is the max speed I can get.

http://forums.macrumors.com/showthread.php?t=1400474

I already have 2 x Vertex 2 120GB in a RAID 0 stripe, and I only get about 300MB/sec from that. So I assume 4 drives will get close to saturation?

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Considering the above, it may be better to simply buy two OWC Eccelsior PCI SSD cards.

One for OS/Apps, and another, 480GB one for data storage/files.

800MB/sec on both.

PS I do everything from Video Editing, Audio Engineering, Web Development, Graphic Design etc.

Specs of my machine in my sig.
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Old Nov 10, 2012, 07:37 AM   #2
JavaTheHut
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I have been thinking about this also ie. 4 ssd in raid. What I concluded was to go the way of a backplane and a Areca Raid Bootable card and get the power from the spare sata cable in the ODD bay2 with the use of a cable split.

This would bring in the sata III speed I believe?
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Old Nov 10, 2012, 07:42 AM   #3
Gav2k
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You will saturate the bus fully. Your best bet is to find out how many it has. I know from pc use some early boards had 1 bus over 2-4 ports later boards had multiple.
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Old Nov 10, 2012, 08:50 AM   #4
Loa
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Hello,

4 SSDs in the bays will pretty much saturate the bandwidth.

As for the 2 Accelsior, you may have to put one of them in the lower slots, because the top 2 slots share the same bandwidth.

Loa
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Old Nov 10, 2012, 11:33 AM   #5
nanofrog
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If they're being used on the MP's SATA ports, the SATA controller tops out at ~660MB/s.

To get past this, you'll have to use a suitable PCIe card (8x lane card for a single model so the data isn't throttled, so not cheap <most of these are actually RAID cards>).

BTW, using RAID 0 is more dangerous to your data than a single disk. This is still the case with an SSD stripe set vs. a single SSD.
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Old Nov 10, 2012, 04:12 PM   #6
scottrichardson
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Quote:
Originally Posted by nanofrog View Post
If they're being used on the MP's SATA ports, the SATA controller tops out at ~660MB/s.

To get past this, you'll have to use a suitable PCIe card (8x lane card for a single model so the data isn't throttled, so not cheap <most of these are actually RAID cards>).

BTW, using RAID 0 is more dangerous to your data than a single disk. This is still the case with an SSD stripe set vs. a single SSD.
I think 660MB a sec is fine for what I need - and I have no issues with the 400% increase in failure potential as it will all be backed up via Time Machine and also regular cloned copies.

At this stage it's either 4 x 120GB SSDs in a 480GB RAID 0 stripe for ~660MB/sec.....

or..

1 x 480GB PCIe OWC Accelsior for about the same speed.

Price difference is $480 vs $750.

----------

Quote:
Originally Posted by Loa View Post
Hello,

4 SSDs in the bays will pretty much saturate the bandwidth.

As for the 2 Accelsior, you may have to put one of them in the lower slots, because the top 2 slots share the same bandwidth.

Loa
Hmm. OK so I have 4 slots total, obviously. GPU in bottom slot. Boot Accelsior in 2nd slot. Files Accelsior in 3rd slot, and my USB3 card in the top slot?
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Old Nov 10, 2012, 04:27 PM   #7
Spacedust
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I've acheived almost 900 MB/s with Areca ARC-1231ML and a Mac Pro 2009



It was about 150 MB/s less on a Mac Pro 2008.
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Old Nov 10, 2012, 04:41 PM   #8
Loa
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Quote:
Originally Posted by scottrichardson View Post
Hmm. OK so I have 4 slots total, obviously. GPU in bottom slot. Boot Accelsior in 2nd slot. Files Accelsior in 3rd slot, and my USB3 card in the top slot?
Nano would be able to answer this question a lot better than I would. :-)

My first guess: put the boot in the slower (3 or 4) slot: work needs more speed than boot.

Loa
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Old Nov 10, 2012, 05:27 PM   #9
scottrichardson
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Quote:
Originally Posted by Spacedust View Post
I've acheived almost 900 MB/s with Areca ARC-1231ML and a Mac Pro 2009

It was about 150 MB/s less on a Mac Pro 2008.
Seems that card is no longer available? Also how did you attach the SSD's? You need to clearly bypass the internal SATA connectors right?
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Old Nov 10, 2012, 06:01 PM   #10
Spacedust
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Quote:
Originally Posted by scottrichardson View Post
Seems that card is no longer available? Also how did you attach the SSD's? You need to clearly bypass the internal SATA connectors right?
It's available on german eBay in a very good price

I've used 1m miniSAS -> 4xSATA cable directly via small hole in optical drive bay into a 6x2,5" backplane instead of second optical drive. Works great and all standard drives will fit too, but you have to put the cable on top of the side of front fan
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