Thanks Hatter, I get the bandwidth difference (well, enough to understand that 2.0 allows more than 1.1/1.0) but I am confused about the 2.0 x 2.
I am wondering if I can install this SSD into my 2nd PCIe slot (2.0 16 band) and get its full benefit. I asked OWC via their blog but only learnt that "the interface is PCIe 2.0 x 2"
Just a value for money question really ... if I get this SSD I will get a performance kick over my current 7200rpm boot and applications drive, just pondering how much.
The Accelsior is a PCIe 2.0 x2 card. The x2 means that the link width can go up to 2 lanes. Physically, the card can fit into any PCI Express slot that can accept an x2 card. Electrically, the card has 2 PCIe 2.0 lanes. Each PCIe 2.0 lane can do 500 MB/s so 2 lanes can do 1000 MB/s which is enough to handle the 2 6Gb/s SATA III SSD's in the Accelsior (700 MB/s).
All PCIe slots in all Mac Pros can physically accept x16 cards. Electrically, the slots are either x1, x4, x8, or x16.
The Mac Pro 2008 has 2 PCIe 2.0 x16 slots (slot 1 and 2). The Accelsior will perform at it's full speed in those slots (PCIe 2.0 x2).
Slots 1 and 2 of the Mac Pro 2006 and 2007 are PCIe 1.0 slots. Each lane in a PCIe 1.0 slot can do 250 MB/s. If you configure the slots to be x8 or x16 using the Expansion Slot Utility, then the Accelsior will do 380 MB/s in those slots (PCIe 1.0 x2).
Slots 3 and 4 of the Mac Pro 2006, 2007, and 2008 are PCIe 1.0 slots. However, when you put an x2 card in slot 3 or 4, only 1 lane will be used because the ESB2 south bridge chip that controls those slots will not negotiate 2 lanes. According to the PCI Express specifications, slots are not required to negotiate a link width of 2 lanes. The Accelsior in slots 3 and 4 only does 195 MB/s (PCIe 1.0 x1).
Correct. The card only takes one slot. A PCIe 2.0 slot (such as slot 2 in the Mac Pro 2008) will give you full performance from the Mercury Accelsior.
Check About This Mac... -> More Info... -> System Report... -> PCI Cards -> pci1b4b,9230. You should see something like this:
Type: AHCI Controller
Driver Installed: Yes
Vendor ID: 0x1b4b
Device ID: 0x9230
Subsystem Vendor ID: 0x1b4b
Subsystem ID: 0x9230
Revision ID: 0x0010
Link Width: x2
Link Speed: 5.0 GT/s
If you see Link Speed: 2.5 GT/s then it means you put the card in a PCIe 1.0 slot.
If you see Link Width: x1 then it means the slot was not able to negotiate 2 lanes to the Accelsior card.
There are a few minor booting issues I've found with the Accelsior in a Mac Pro 2008 (minor if you don't care about Boot Camp):
If I hold option key down during startup to see the Startup Manager, then the Startup Manager will not show the partitions on the Accelsior. This means I can't use Recovery HD from the Accelsior. I need to keep an OS on a normal hard drive for emergencies.
I am unable to boot Windows or Linux (using Boot Camp) from a CD/DVD, from a hard drive, or from the Accelsior, while the Accelsior is installed. This means I can only use virtualization software (such as Parallels Desktop) to run Windows.
If I boot rEFIt or rEFInd from the Accelsior, then they will not show partitions from other hard drives. If I boot rEFIt or rEFInd from a hard drive, they will not show partitions on the Accelsior.
That has been my experience on the Mac Pro 2008. I have been unable to use my Boot Camp partitions no matter where they are located unless I remove the Accelsior.
I haven't found any other users that have noted success or failure with Boot Camp on the old Mac Pros (2006, 2007, 2008) with the Accelsior card installed.
I can still use Parallels Desktop for Mac to boot my Boot Camp partitions while running Mac OS X though.
I received 2 of these cards the day OWC made them available.
FWIW my benchmarking was in the ballpark of the published MPG numbers but not identical.
I have them both installed on a 2010 MacPro. They worked fine on SL & now on Lion.
Downside: I cold not get Lion to install on a RAID-0 config of both drives. The install barfed.
Instead, I partitioned both cards to give me ~80GB boot partition on 1 card, another ~80GB partition on the other card and then I created a stripe-0 volume across the other ~40GB partitions on each card giving me 3 ~80GB partitions.
Here's the numbers for both the ~80GB scratch disk & the ~80GB RAID-0 partition:-
Using test size of 2GB, 4MB at a time at start (0%), within a 72.0GB test file.
Iteration 1: writing…673MB/sec, reading…685MB/sec
Iteration 2: writing…662MB/sec, reading…686MB/sec
Iteration 3: writing…670MB/sec, reading…684MB/sec
Iteration 4: writing…671MB/sec, reading…688MB/sec
Iteration 5: writing…670MB/sec, reading…688MB/sec
Monday, May 28, 2012 3:12:33 PM Pacific Daylight Time, volume "Accelsior-Single" (74.4GB)
------------ Averages for "Accelsior-Single" (2GB/4MB, 5 iterations) -----------
Iteration Write MB/sec Read MB/sec
1 673 685
2 662 686
3 670 684
4 671 688
5 670 688
Slowest 662 684
Fastest 673 688
Average 669 686
Median 670 686
Range 11.7 4.49
Command "run-sequential" executed in 31.00 seconds on Monday, May 28, 2012 3:13:04 PM Pacific Daylight Time
Using test size of 2GB, 4MB at a time at start (0%), within a 71.2GB test file.
Iteration 1: writing…1234MB/sec, reading…1269MB/sec
Iteration 2: writing…1184MB/sec, reading…1265MB/sec
Iteration 3: writing…1182MB/sec, reading…1288MB/sec
Iteration 4: writing…1172MB/sec, reading…1267MB/sec
Iteration 5: writing…1171MB/sec, reading…1276MB/sec
Monday, May 28, 2012 3:13:18 PM Pacific Daylight Time, volume "Accelsior-RAID" (73.6GB)
------------- Averages for "Accelsior-RAID" (2GB/4MB, 5 iterations) ------------
Iteration Write MB/sec Read MB/sec
1 1234 1269
2 1184 1265
3 1182 1288
4 1172 1267
5 1171 1276
Slowest 1171 1265
Fastest 1234 1288
Average 1189 1273
Median 1182 1269
Range 63.6 22.1
Command "run-sequential" executed in 17.10 seconds on Monday, May 28, 2012 3:13:35 PM Pacific Daylight Time
You can see that RAIDing these cards boosts your "full-performance" very nicely... almost twice as fast.
One other thing, contrary to other posts, I am able to boot from a separate SSD into Windows just fine... except it takes 7.5 minutes to boot. Once booted Windows runs fine. Boot time for OS X also increases when the Accelsior cards are installed (just like other PCIe SSD cards).
I expect a third Accelsior would boost "full-performance" higher... MPG posted a few details on there findings, but not until after I tested it for myself by RAIDing 2 Accelsiors with an OCZ Revo Drive (also a PCIe card).
My results again were in the ball park that MPG posted, but I did get better visibility as to performance ranges that MPG did not publish by using benchmarks available through Windows.
So to answer someone els's Q, no you should not have to physically remove your Accelsior cards in order to boot into Windows from a separate drive.
Not sure what you mean.
> did your mix of two different cards affect your tests?
I was providing info rather than asking Q's.
The test results I quoted were only from:
(1) a single Accelsior partition on a single card
(2) a single Accelsior RAID-0 volume striped from 2 identical Accelsior cards.
I think the test results are within the same ballpark as MPG (actually maybe a bit better than their published results).
> creaating an array to boot from?
Given the far superior results when putting 2 Accelsiors into a RAID-0 config then why wouldn't I try this given OWC claims the cards are bootable. Actually, the Lion installation thought it could do this since it gave a warning that since my boot drive was a RAID config some features wouldnt be available, such as filevault... the installer was still quite happy to waster over an hour with me "doing the installation" to my Accelsior RAID boot drive, before it decided to declare it failed.
> perhaps try with just the two Accelsiors?
Try the installation with just the 2 Accelsiors? Thats what did not work, but I got past that limitation.
Like I said I got Lion installed using partition #1 of Accelsior #1.
I created a SingleAccelsior partition #1 on Accelsior #2.
I created a RAID-0 volume combining both partitions #2 from Accelsior #1 & #2.
This all worked and what the performance results I showed represent.
Not sure what it is that I should try ... the Windows partition that does install is on a separate SSD.
I mentioned this since I read in this thread claims that Windows couldnt boot if the Accelsiors were installed & I was informing those posters that it is possible.
There are various ways to get Lion on a software RAID. It just takes a little extra work.
When you create a raid set, Disk Utility automatically adds an Apple_Boot partition called "Boot OS X" to each hard disk. The "Boot OS X" partition is used to boot OS X when it's installed on a raid set. The only thing left for you to do is to get OS X onto the raid set. The Lion installer sometimes fails at that because of the Recovery HD. I think the simplest method may be to use Disk Utility's Recover option to copy your existing Lion partition to the raid set. If you use Recover from Disk Utility to copy a Lion partition, it will also try to copy the associated Recovery HD partition as well if it exists. This won't work when the destination partition is a raid set. The workaround is to use Carbon Copy Cloner instead, or temporarily change the partition type of the Recovery HD partition from Apple_Boot to Apple_HFS using iPartition, gpt fdisk (gdisk or cgdisk http://sourceforge.net/projects/gptfdisk/ ), or gpt. Once the Restore is complete, you can revert the partition type of the Recovery HD back to Apple_Boot.
The problems I'm having with Boot Camp and the Accelsior probably have to do with the older EFI firmware of the Mac Pro 2008. Apple doesn't make firmware updates for older Macs. I'm waiting for someone with a 2006, 2007, or 2008 Mac Pro to chime in on Boot Camp issues.
I haven't found a solution for running Boot Camp while the Accelsior is installed in my Mac Pro 2008. I also haven't found any other complaints about Boot Camp with the Accelsior SSD either. Actually one person with a Mac Pro 2009 with an Accelsior says it took 15 minutes for Windows to appear but the description of the problem was missing some details. Windows does not appear if I wait 15 minutes or an hour. Another Mac Pro 2009 user has no problem booting Windows from a SATA drive when an Accelsior is installed.
OWC has not explicetly confirmed or denied this Boot Camp incompatibility with the old Mac Pros on any website but they did add my user rating/review that mentions the problem to their Accelsior 480 GB page.
Have you purchased the card? What kind of Mac do you have? Are you experiencing issues?
I'm thinking the solution might involve rewriting some Compatibility Support Module (CSM) stuff in EFI so that it ***** less on the old Mac Pros.