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2x P256 in MacBook Pro 5,5 (13", 2.53GHz)…*pausing!


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Hey everyone,


Had a single P256 in my previous MBPro, recently moved it over to this new 13" MacBook Pro (2.53GHz C2D, 4GB RAM, 10.5.8). Performance was always awesome.


Yesterday, picked up a second P256, to stick into the optical bay.


After RAIDing them (RAID 0, courtesy of Disk Utility), I noticed that despite the increase in benchmark performance, the entire RAID would pause for 10-25 seconds during large file operations.


During my troubleshooting, I split them back into separate drives, and noticed something peculiar. Having two of these drives on the SATA bus, one would always pause during file operations!


I have not been able to determine what the cause is. No I/O errors, no logging or anything - they behave as they should, but just one always pauses. And it looks unrelated to what motherboard connector they're using: my original drive remains on the same SATA connector it's always been on, yet with the introduction of the new drive on the second SATA connector, it's the original one that pauses - while the new one remains perfectly fast.


For me, this is not a huge issue, as I just needed more storage in general, not necessarily a RAID - so for static storage, I can deal with a bit of pausing until I can get this sorted out. Smells like some sort of conflict/wonkiness/whatever in the motherboard, as both drives on their own are perfectly fast and stable.


If anyone has similar experience, would love to hear about it - but for now, consider this a heads-up! =)

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Actually I did, on another MBPro. Also on my own MBPro, I tried each drive on each SATA connector - and with two drives on the bus, it looks like it's always the one that is downstream, that pauses.


For example - currently, since I need to use my computer and all, my boot drive is on the former optical drive SATA connector, and is disk0s2. This is the brand new drive, and works perfectly. My old drive remains in the same place it always was - in the drive bay - and is disk1s2. This is the drive that now has the pausing during file operations.


The testing that I did, involved switching the connectors around - so the new drive was on the drive bay SATA, and the old drive was on the optical drive SATA. In this case, the situation changed so that the NEW drive was the one with the pausing.


Quite odd, I must say. And both drives work perfectly well on their own - nearly identical, aside from a tiny bit of slower performance on the old drive (though it still hits 200+ on Xbench tests).

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If I understand your post correctly that would suggest it is the controller on the NB that may be the cause, have you spoke to apple to see if there are any known issues and or updates to the firmware to address this?
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Okay, heard back. Without breaking NDA, I can simply say that Apple qualifies/supports the second SATA channel (that is, the optical drive one) for use with optical drives only.


Whelp, let this be a heads-up to anyone interested in reproducing my setup!

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Oh one more thing - I'm going to tinker this weekend to make doubly-sure that both drives are operating at 100% independently. After talking to other folks that had done similar setups (2x SSDs in Unibody MBPros), none has experienced this pausing issue - although, none were using the same hardware as I am. Hmm!
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POTENTIAL solution:


From some more testing, cloning the OS and drive swapping, it looks like the solution may be this:


At least in the recent Unibody MacBook Pros, the boot volume HAS to be in the DRIVE BAY.


Even though the low-level drive numbering remains the same (boot drive is disk0, secondary drive is disk1), now with the OS installed on the drive connected to the DRIVE SATA port, there's no longer any pausng problem with the secondary drive.


Go figure. I'm gong to do more testing when I get home before attempting RAIDing them again, but this is very promising! If all goes well I'llpost the resulting RAID benchmarks!

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Okay! So I ended up forgoing a RAID configuration. Overall, Xbench score was between 210 and 250 (see below single-drive results to put this in context) depending on current OS-level idle operations. Impressive, for a machine with midrange specs and running Apple's software RAID.


A few reasons I'm leaving them as independent drives:


- Dual internal drives aren't supported by Apple for good reason: in this machine, a RAID will disable Safe Sleep mode (the default sleep mode). Instead, it will just keep the RAM powered. The battery drain is really minimal, but in terms of data integrity, it made me a bit uncomfortable.


- I prefer to "spread out." That is, having iTunes and iPhoto libraries on their own little directory on the secondary SSD, using it for a bunch of Xcode projects, and so forth. Personal preference - I'm just better organized this way.


Anyway, for the heck of it, my results on the boot SSD are attached below. This was taken while booted off the drive - running the bench while booted off an external drive obviously ups the score consistently by around 10; in general though, repeated test results vary by about +/- 5 points.


For anyone on the fence on getting even one of the P256 drives, my favorite quickie, non-scientific timings:


- Boot time, from screen power on to login window: no more than 9 seconds. Seriously. That is insane. I've been in IT for a lifetime and have never seen anything like that. No matter what the machine's specs are, this drive will have it booted in a sick amount of time. (I had the SSD in a loaded 17" Unibody MBPro originally, and it was even faster, FYI!)


- Unrar'ing an 800MB file (about 50 parts): 10 seconds.


- Launching Photoshop CS4: 3.5 seconds.


- Launching Safari: too fast to even calculate.


- Launching iPhoto, 6GB photo database: 0.5 seconds.


It's simply nuts.


Bonus! Replacing the optical drive with the second SSD makes the machine noticeable lighter. Not a huge amount, but enough to be hugely appreciated. Both drives run ice cold, no noticeable drain on battery life (though I'm sure there's a bit).


Can't say enough good things about my experience with these Corsair drives, they simply can't be beat.


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