Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
4 Drive SSD RAID 0 Mac Pro 5,1
- Thread starter riggieri
- Start date
- Sort by reaction score
SATA II LIMIT IS 3gb per channel and this is over four channels. I guess the apple backplane and controller are hitting about maximum on this anyways.
1) Your SSD may have only 150MB/s, some smaller (e.g. 250G SATA SSD) only has this write speed. Therefore, 4x150=600
2) For some better SATA SSD, may hit the 250MB/s read/write speed bottleneck due to SATA 2 limitation. So, the best you can achieve is about 1000MB/s, no way to achieve 1.2GB/s
For high speed storage, simply get a PCIe SSD is a better way, 4 SSD in RAID 0 means 4x the failure rate, and the best you can achieve is just about 50% of a single PCIe SSD can do. So why take the risk but not go for simpler setup which have better performance?
2) For some better SATA SSD, may hit the 250MB/s read/write speed bottleneck due to SATA 2 limitation. So, the best you can achieve is about 1000MB/s, no way to achieve 1.2GB/s
For high speed storage, simply get a PCIe SSD is a better way, 4 SSD in RAID 0 means 4x the failure rate, and the best you can achieve is just about 50% of a single PCIe SSD can do. So why take the risk but not go for simpler setup which have better performance?
255MB/s on a Samsung 850 Pro 512GB here. Definitely not more on SATA2.
But yes, that's one channel.
S
So, all 6 ports share that 660MB/s? I have absolutely no idea about this, may I know any reference for that. Nothing offensive, just want to know the truth.
So, all 6 ports share that 660MB/s? I have absolutely no idea about this, may I know any reference for that. Nothing offensive, just want to know the truth.
cMP have an aggregate SATA backplane upper throughput limit of about 650 MB/s , across the four drive connectors . It's host computer chipset related , not drive related per se . That's why it doesn't make much performance difference between using SSD and HDD in this situation .
Solution is to grab a mini SAS PCIe card and internally mount the SSDs in your Mac Pro . OWC has a Newer Technology card .
http://eshop.macsales.com/item/NewerTech/MXPRMS6G1E1I/
Last edited:
Yep, and use a MaxConnect to connect the drives using the existing SATA power in the backplane.
http://www.maxupgrades.com/istore/index.cfm?fuseaction=category.display&category_ID=351
"Yep, and use a MaxConnect to connect the drives using the existing SATA power in the backplane."
Maxupgrades has a confusing website , but I think the OP's situation requires this kit to mount four SSDs in his Nehalem cMP :
http://www.maxupgrades.com/istore/index.cfm?fuseaction=product.display&product_ID=189&ParentCat=351
HBA card is not included in the price - it's just for the special sled adapters (and I assume the fan out mini SAS cable) for four SSD .
Maxupgrades has a confusing website , but I think the OP's situation requires this kit to mount four SSDs in his Nehalem cMP :
http://www.maxupgrades.com/istore/index.cfm?fuseaction=product.display&product_ID=189&ParentCat=351
HBA card is not included in the price - it's just for the special sled adapters (and I assume the fan out mini SAS cable) for four SSD .
Depends if the OP needs a 12Gbps or 6Gbps fan out cable
Your link is for a 6Gbps cable.
And yes, their website is HORRIBLE.
Depends if the OP needs a 12Gbps or 6Gbps fan out cable
Your link is for a 6Gbps cable.
And yes, their website is HORRIBLE.
The OWC Newer Technology RAID card I linked is 6 Gb/s , so that would be the limiting factor .
And the OP's SSDs are likely non-enterprise grade 6 Gb/s SATA .
Areca does have a 12 Gb/s mini SAS RAID card ( ARC-1883LP ) compatible with OS X 10.11 El Capitan , with an internal connector :
http://www.areca.com.tw/products/1883.htm
Things do get more expensive with everything at 12 Gb/s , of course .
The throughput he desires (around 1100 MB/s) can be achieved with three x 6 Gb/s SSD in the array , Since the OWC Newer Technology card is not bootable in OS X , that would leave one SATA backplane available for a separate drive with an OS X install .
Your link is for a 6Gbps cable.
And yes, their website is HORRIBLE.
The OWC Newer Technology RAID card I linked is 6 Gb/s , so that would be the limiting factor .
And the OP's SSDs are likely non-enterprise grade 6 Gb/s SATA .
Areca does have a 12 Gb/s mini SAS RAID card ( ARC-1883LP ) compatible with OS X 10.11 El Capitan , with an internal connector :
http://www.areca.com.tw/products/1883.htm
Things do get more expensive with everything at 12 Gb/s , of course .
The throughput he desires (around 1100 MB/s) can be achieved with three x 6 Gb/s SSD in the array , Since the OWC Newer Technology card is not bootable in OS X , that would leave one SATA backplane available for a separate drive with an OS X install .
Possibly not enough PCIe lanes allocated to the on-board SATA controller(s) to run all channels flat out at the same time.
The classic mac pro was designed in a time where SSD was rare and super expensive, it wasn't really expected to deal with devices that can saturate the SATA bus to the extent that SSDs can. When the older Mac Pro came out allocating 1:1 bandwidth in terms of PCIe -> max SATA channel speed would have been a waste.
Can maybe get around this with a PCIe card.
The classic mac pro was designed in a time where SSD was rare and super expensive, it wasn't really expected to deal with devices that can saturate the SATA bus to the extent that SSDs can. When the older Mac Pro came out allocating 1:1 bandwidth in terms of PCIe -> max SATA channel speed would have been a waste.
Can maybe get around this with a PCIe card.
I just happened to think that for very high end bandwidth requirements , installing a mini SAS RAID card would require PCIe Slot 2 installation in a Nehalem cMP . A lot of these cards require 8 lanes electrical and at PCIe Rev 2 specs this would provide 8 x 500 MB/s ( = 4 GB/s) performance , minus any overhead .
It's more complicated than that since Southbridge has a x4 connection for everything, so it's seriously limited. People tested this in the past and even if you RAID all 6-SATA ports, you can't get over 550~600MB/s. BTW, 4 SATA ports or 6 SATA ports get the same results.
Apple new this from the start, AppleRAID card is connected directly to PCIe.
Everything = SATA/SAS, USB, Ethernet, Wi-Fi, Firewire, SMC, Audio.
That's true, the final possible speed depends on the wifi, ethernet, audio, bluetooth.... etc.
It's impossible to achieve full 1500MB/s in real world.
But I am not sure what's the actual limit. I think someone achieved 750MB/s before, but not really sure.
In fact, I wonder what will happen if someone do the disk speed test (e.g. BlackMagic), then shutdown / disable those things attach to the southbridge one by one
In the past someone tested this, removing the AirPort Extreme, the only thing that you can really be removed and didn't change anything. There are even more things connected than I listed, like GPIO, I2C, RTC, LPC, APIC and others, I previously listed the bandwidth hogs.That's true, the final possible speed depends on the wifi, ethernet, audio, bluetooth.... etc.
It's impossible to achieve full 1500MB/s in real world.
But I am not sure what's the actual limit. I think someone achieved 750MB/s before, but not really sure.
In fact, I wonder what will happen if someone do the disk speed test (e.g. BlackMagic), then shutdown / disable those things attach to the southbridge one by one
I can be wrong, but I remember that sustained speeds are around 550MB/s mark with a little more for peaks, but never saw 750MB/s. Remember that the IC10 south bridge is from third quarter of 2008, at the time the best HDDs were around the 100MB/s mark.
I get between 630 and 680 MB/s with three Samsung 860 EVO in the cMP SATA slots.