Fusion Drive Questions

[jruschme]

I recently came into possession of a 64GB SSD from a friend who was upgrading. Since this is my first SSD, I've been kicking around various ideas about how best to use it. One idea which has really stuck with me is using it and an optical drive caddy to upgrade my mid-2009 MBP with a Fusion Drive. A few questions, though:

1) Is a fusion drive worthwhile in an MBP? Any gotchas, especially with sleep?
2) Is a fusion drive worth it with only 64GB of SSD? I figure that it is enough for the OS and frequently used apps/files, so I'd think it would be beneficial.

Thoughts?

Thanks in advance...

 

[Dark Dragoon]

1) Sleep and everything else works fine with a Fusion Drive in my mid-2010 MBP. It is definitely worthwhile for me.

2) It's a bit small, I used to use a 96GB SSD as part of a Fusion Drive (before getting a bigger SSD) and it certainly sped things up. All it means is that your most accessed 64GB would be on the SSD, so it depends on how much your workflow changes day to day and how many applications you use.

As you already have the SSD, and an optibay is cheap. I'd give it a go.

 

[jruschme]

Well, I installed it all yesterday (and spent all night restoring my system); so far it seems a bit "uneven". Some things really fly, but others seem slower than when I had the single drive.

Any idea how long it takes to "break in" a fusion drive?

 

[Dark Dragoon]

Personally I wouldn't have just dumped all the data on the drive in one go, as that may cause it to take longer to sort itself out.

It shouldn't feel slower than if you were using a single drive, I would check to make sure it is working correctly. To do so first run the following in Terminal:

diskuti list

Note the number of the two drives that make up your Fusion drive, for example on mine the SSD is "/dev/disk0" and the hard drive is "/dev/disk1", thus "disk0" and "disk1".

Next run the following from the Terminal:

iostat disk0 disk1 1

Where disk0 and disk1 are your SSD and HDD from the previous command.

The reading should be 0 or fairly low for both drives. If it isn't it may still be transferring data between the drives so you would want to leave the computer running to let it finish up moving the data around.

If this isn't the case, leave the Terminal open with iostat running and try and open some applications you frequently use.
Check which drive is accessed, you should see one of the disks being accessed. Check to make sure it is the SSD and not the hard drive.

In the past at-least certainly with Mavericks and maybe Yosemite there has been problems with creating a Fusion Drive which means that depending on how you create it, it can work the wrong way round where all the most frequently used data is placed on the HDD, or it just doesn't create a proper Fusion Drive at all so it doesn't move any of the data around.

 

[Dark Void]

Depending on what you do and how many applications you have, 64 GB could be enough for all of your system files and applications, or at least a number of them.

I'd suggest anything media related to be stored on the mechanical portion, and all (or as many as you can) applications and system files (OS X image) to be stored on the SSD. It will be worth it as you will have increased boot times and read/write speeds with anything stored on the drive.

 

[Dark Dragoon]

I'd suggest anything media related to be stored on the mechanical portion, and all (or as many as you can) applications and system files (OS X image) to be stored on the SSD. It will be worth it as you will have increased boot times and read/write speeds with anything stored on the drive.

This is essentially what the Fusion Drive does automatically, at-least it does when it is working correctly and after you have used your computer for a little while so it can figure out what data you access most frequently.

You don't need to choose where to put the files as it handles all that for you.

 

[Dark Void]

This is essentially what the Fusion Drive does automatically, at-least it does when it is working correctly and after you have used your computer for a little while so it can figure out what data you access most frequently.

You don't need to choose where to put the files as it handles all that for you.

I'm sorry, I misread, I thought the OP was looking to use the SSD and a mechanical drive in the optical bay just as more inactive disk space.

 

[jruschme]

Next run the following from the Terminal:

iostat disk0 disk1 1

Where disk0 and disk1 are your SSD and HDD from the previous command.

The reading should be 0 or fairly low for both drives. If it isn't it may still be transferring data between the drives so you would want to leave the computer running to let it finish up moving the data around.

If this isn't the case, leave the Terminal open with iostat running and try and open some applications you frequently use.
Check which drive is accessed, you should see one of the disks being accessed. Check to make sure it is the SSD and not the hard drive.

In the past at-least certainly with Mavericks and maybe Yosemite there has been problems with creating a Fusion Drive which means that depending on how you create it, it can work the wrong way round where all the most frequently used data is placed on the HDD, or it just doesn't create a proper Fusion Drive at all so it doesn't move any of the data around.

According to instate, it's definitely hitting the SSD more than the HDD, so the setup is correct (diskutil info confirms that it is a fusion drive). I'd guess that my problem (if any) is from the restore and that it's probably going to take a while to sort out my workflow.

Thanks for the help...

 

[jruschme]

Well, I found my performance issue. It seems that the mid-2009 MacBook Pros had an EFI update (1.7) which gave them the ability to negotiate SATA II transfer speeds (3 Gigabit). However, apparently they really don't support SATA II speed correctly on an device in the optical bay. This leaves me one of three options:

1) Give up the fusion drive idea.
2) Downgrade to EFI update 1.6 which limits me to SATA I speeds (1.5 Gigabit)
3) Use a genuine Apple ROM HDD in the optical bay since those are firmware locked to 1.5 Gigabit (same as option 2, but I can use a non-Apple drive and/or put the SSD in the optical bay with that option)

For now, I've decided to forgo the fusion drive and put everything back as it was.