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Resolved Mac Pro SSD Raid

D

DenBeke

macrumors regular
Original poster
Aug 11, 2011
192
8
Antwerp
Hello,

I'm planning to place an SSD RAID 0 in my Mac Pro.
Will this RAID really improve performance? So if I place two SSDs at 500MB/s write each, will I reach 1GB/s for the raid?

Is it possible to use a software raid as boot disk?
Or is it way better (or faster) to buy a RAID controller? (And if I need a RAID controller, must it then be the Apple's raid controller?)
 
Last edited:
DenBeke said:
Hello,

I'm planning to place an SSD RAID 0 in my Mac Pro.
Will this RAID really improve performance? So if I place two SSDs at 500MB/s write each, will I reach 1GB/s for the raid?

Is it possible to use a software raid as boot disk?
Or is it way better (or faster) to buy a RAID controller? (And if I need a RAID controller, must it then be the Apple's raid controller?)
Click to expand...

Mac Pro is SATA2 only without PCI expansion card. 2x500MB/s SSD's will net you 500-550MB/s. You can buy any Mac compatible RAID controller but you still will not see 1GB/s as the PCI bandwidth is capped. Do you really need 1GB/s? Get a controller with at least 4x PCI lanes. ATTO and Areca are good bets.
 
I don't really need 1GB/s, but I wanted to know if having 2 SSD's in a RAID will double the read/write speed?

BTW: Thank you for this answer!
 
DenBeke said:
I don't really need 1GB/s, but I wanted to know if having 2 SSD's in a RAID will double the read/write speed?

BTW: Thank you for this answer!
Click to expand...

Sequential read/write speeds do scale linearly with the number of drives in RAID0. However, the limiting factor in a Mac Pro when running SSD's can be a few things (and not usually the performance of the drive). SATA2 maxes out at around 250MB/s. The ICH maxes out at around 660MB/s and a dual lane PCIe card maxes out at around 600-800MB/s depending on the card. So if you run a pair of current gen SSD's in RAID0 you will double the sequential read/write performance but it will only be double the minimum of any of your limiting factors.

At any rate, a RAID0 array won't hurt (as long as you backup your data which you would do regardless of RAID or not). It could improve performance... whether it's noticable or not is another thing... and it does allow you to combine two potentially cheaper drives to make a single large higher performing storage volume.

And OS X makes SW RAID0 arrays easy... just use disk utility to add disks to your array and format it.
 
VirtualRain said:
The ICH maxes out at around 660MB/s
Click to expand...

The I/O Controller Hub, is that the bottleneck for all storage and other devices?
So the total of internal HDD's, Disk Drives, PCIe cards, USB/FW Disks, can't go over 660MB/s?
Or is internal I/O directly attached to the logic board and thus not bottlenecked by the ICH?

I'm sorry, I'm not really into the total technic side of my Mac Pro...
 
I am running a pair of 3G OWC 240 GB SSDs as RAID-0 in my Mac Pro 2008 3,1. They are bracket mounted in the optical bay and connected to the spare SATA-II ports on the motherboard. They boot fine and run fast.

See the attached .pdf file for AJA test (how do you display .pdf files here?) AJA shows higher performance at 500MB/s than the BlackMagicDesign with Sandforce controllers.

-howard
 

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DenBeke said:
The I/O Controller Hub, is that the bottleneck for all storage and other devices?
So the total of internal HDD's, Disk Drives, PCIe cards, USB/FW Disks, can't go over 660MB/s?
Or is internal I/O directly attached to the logic board and thus not bottlenecked by the ICH?

I'm sorry, I'm not really into the total technic side of my Mac Pro...
Click to expand...

The ICH bottleneck I mentioned of 660MB/s applies to total SATA throughput. For example, I have 3 older SATA2 SSD's running through the backplane SATA ports in RAID0 and I'm limited by this ICH bottleneck. The way around this is to use a PCIe card but then it's really difficult to find SATA3 PCIe cards that are not bottlenecked in some way also (and that are bootable/supported in a Mac). Most are dual lane cards which will throttle a pair of modern SATA3 SSD's in RAID0. I recently ordered this 8x PCIe SATA3 card which I'm hoping can give me full speed on a trio of SSDs for data, but it's not bootable...

http://www.newegg.ca/Product/Product.aspx?Item=N82E16816115100

To boot, the best option seems to be this, but it's a dual lane card meaning it's really only going to work with a single SSD without throttling... (not to mention cabling a 2nd drive is a PITA with this)

http://www.apricorn.com/products/desktop-ssd-hdd-upgrade-kits/vel-solox2.html

The bottom line is that there doesn't appear to be a card that is affordable, bootable, and not bottlenecked for multiple SATA3 SSD's in RAID0 :(
 
I would just install one SSD with your prefered size and fine. For daily use one SSD has enough performance even on SATA 2. The important little read/write operations usually don't even reach the SATA 2 limit. So just go for one fast ssd, which can be used hassle free.
 
Conclusion:

2 SSD's in a RAID 0 would be perfect. Since we mostly write/read small files, two SSD's will never reach the ICH bottleneck speed. (And hopefully not all I/O together...)


New question:

Where to find more information about this mysterious I/O Controller Hub?
You talk about 660 MB/s max speed. But what about Thunderbolt, which goes with 10Gbit way over your 660Mbyte/s.
How can they write with a MBA at 1Gbyte/s to a TB RAID?

Where can you find the exact ICH of your Mac?
 
Last edited:
Hi all,

I've seen the guide in post 1, but I'm a bit confused. Can anyone recommend a PCIe adaptor that would give me faster speeds than my Lycom DT-120, without spending huge amounts of cash (say less than £100?)

Or it would also be great if there was a card that accepts multiple NVMe drives, I don't care about RAID. I've just got my other PCIe slots full.

I currently have the 'old standard' - a 256GB Samsung SM951 AHCI (as boot drive). I've added a heatsink to it (didn't seem to make much difference). I get about 1100MB/sec write and 1400 read. I'm thinking of getting a 512GB or 1TB NVME drive but wouldn't bother if it's not going to give me better performance as well as more capacity.

I am running a 4,1 -> 5,1 on Mojave, Boot Rom 144.0.0.0.0, and Open Core.

Amazon currently have 1TB WD 750 Black on offer, about 25% off.

Cheers,

Ed
 
Last edited:
Sharky II said:
Hi all,

I've seen the guide in post 1, but I'm a bit confused. Can anyone recommend a PCIe adaptor that would give me faster speeds than my Lycom DT-120, without spending huge amounts of cash (less than £100?)

Or it would be great if there was a card that accepts multiple NVMe drives, I don't care about RAID. I've just got my other PCIe slots full.
Click to expand...
About the throughput:

To overcome the PCIe v2.0 throughput limit of ~1500MB/s for a x4 device installed in a MP5,1, all M.2 devices have just 4 PCIe lanes, you need a PCIe switched card to convert x16 PCIe v2.0 into x4 PCIe v3.0.


Bifurcation/cheap multiple M.2 adapters:

What you want is just impossible, since no Mac (even 2019 Mac Pro) has support for Intel PCIe Lane Partitioning, aka bifurcation.

All Mac Pros before the 2019 Mac Pro have chipsets too old to support it, while 2019 Mac Pro have a compatible chipset but don't have the firmware and MUX hardware support needed for bifurcation to work.

Read the first post of the thread below:

forums.macrumors.com

PCIe SSDs - NVMe & AHCI

This is a general info thread for blade SSDs that can be used in the Mac Pro. This is a WikiPost so anyone with the proper credentials may edit it. NVMe SSDs can be used as a boot drive in the MP5,1 and MP6,1 with the latest firmware installed (beginning with version 140.0.0.0.0 for MP5,1 and...
forums.macrumors.com forums.macrumors.com
 
Last edited:
Thanks for your reply - I have to admit I actually thought I was posting in a different thread, so apologies to the OP for hijacking!

tsialex said:
About the throughput:

To overcome the PCIe v2.0 throughput limit of ~1500MB/s for a x4 device installed in a MP5,1, all M.2 devices have just 4 PCIe lanes, you need a PCIe switched card to convert x16 PCIe v2.0 into x4 PCIe v3.0.
Click to expand...

Yes, I suppose I'm wondering which specific cards support that and is still being sold...

tsialex said:
Bifurcation/cheap multiple M.2 adapters:

What you want is just impossible, since no Mac (even 2019 Mac Pro) has support for Intel PCIe Lane Partitioning, aka bifurcation.

All Mac Pros before the 2019 Mac Pro have chipsets too old to support it, while 2019 Mac Pro have a compatible chipset but don't have the firmware and MUX hardware support needed for bifurcation to work.

Read the first post of the thread below:

forums.macrumors.com

PCIe SSDs - NVMe & AHCI

This is a general info thread for blade SSDs that can be used in the Mac Pro. This is a WikiPost so anyone with the proper credentials may edit it. NVMe SSDs can be used as a boot drive in the MP5,1 and MP6,1 with the latest firmware installed (beginning with version 140.0.0.0.0 for MP5,1 and...
forums.macrumors.com forums.macrumors.com
Click to expand...

Okay, thank you! I actually thought I was posting in the thread you linked, I have read that.

Apologies again for posting in the wrong thread

Cheers,

Eddie
 
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