Merge 2 SSDs into a fusion drive (Core Storage)

Question

Level 1

9 points

Merge 2 SSDs into a fusion drive (Core Storage)

Hello.

Since I can't reply to this thread Merge 2 SSDs into Core Storage (Fusion Drive) possibly because I'm new, I'm doing it here.

To anyone owning two SSDs, and curious how do they perform in a fusion drive config I want to suggest just testing it.

I saw replies stating that it's "not recommended", but not a one post saying that someone has actually tested it.

I just did.

I have installed my two SSDs, Samsung EVO 250, and 500, as a fusion system drive. The projects I keep on the HDD.

What I have discovered is the exact opposite to what has been recommended.

The overall speed of the system increased significantly, which is logical since the idea of the fusion drive ( as far as I have learned ) is to scatter data across two physicals drives.

All the heavy projects (600-800 MB) are loading +/- twice as fast comparing to a single SSD system drive I had before.

So far so good.

I suppose that in time the system will get cluttered, and so the performance will drop a bit, but we have tools for this.

I will try to keep you posted on how its going... maybe.

Cheers.

Posted on Nov 27, 2018 12:56 AM

Reply

Answer 1

Top-ranking reply

Glen Doggett

Level 4

2,759 points

Nov 28, 2018 8:49 PM in response to Hazooka

There are RAID options for combining drives that may perform better than an SSD-only-Fusion, but I am not really familiar with how the Fusion drives work. I think the scheme for Fusion assumes you have one small fast drive SSD and one slower larger drive RPM. The Fusion scheme tries to balance speed and performance by placing more frequently used data on the smaller faster drive and migrating seldom used data to the larger slower drive. If both drives are equally fast, then other methods for joining the drives may perform better since you don't have the overhead of the Fusion method of selecting what data goes where and moving it.

RAID-0, or striped raid, is ideal for two fast drives on their own separate fast channels that are the same size (or when different sizes are combined you only get the combined RAID-0 drive of size equal to twice the smaller drive, I think) You would not want to have RAID-0 drives sharing a cable, i.e. daisy chained from one single USB port, for example, but have each drive on its own connection to the computer.

I think a RAID-0 would perform better than a Fusion drive using same size identical SSD pair of drives, but I have not tried this comparison myself. I think if you RAID-0 a pair of SSD drives, it's like putting instant coffee in a microwave, you may just go back in time since it is so fast. 🙂

If you have two different sized fast drives and want to combine them into one larger drive, a "RAID" of type JBOD, just a bunch of discs kind of a misnomer, since not really a RAID, is a way to combine the drives into one larger drive, it will not really be any faster than either single drive on its own.

Hard drives are getting cheaper and faster. When you have a RAID-0 drive fail, since the data is scattered across the two drives, all data would be lost. I am not sure how a failure of one of the drives in a Fusion set up would impact you. Backup, backup, backup. Keep an up-to-date bootable backup on an external drive. Update the backup before you install any system updates.

Reply

Answer 2

dialabrain

Level 10

136,325 points

Nov 27, 2018 1:34 AM in response to Hazooka

Two things, you can't reply to the thread because it's locked, not because you're new. The last thing is, all one can say about an SSD/SSD Fusion drive is it would be faster than a SSD/HDD Fusion drive. The only reason a SSD/SSD Fusion drive would be faster than a SSD drive alone would be the the slowest SSD in the SSD/SSD Fusion drive was fater than the SSD drive alone.

Reply

Answer 3

Hazooka Author

Level 1

9 points

Nov 27, 2018 2:08 AM in response to dialabrain

I have two drives, with the same read/write specs, working as one. They are as fast.

I don't think the capacity of the SSD drive has anything to do here. With HDD it would matter most likely. For an SSD speed matters.

I can only see one logical cause for this set being faster - the data scatter.

For the end user though the technical details don't matter.

It's faster, that's what matters.

Cheers.

Reply

Answer 4

Hazooka Author

Level 1

9 points

Nov 28, 2018 10:22 PM in response to Glen Doggett

Yes, backup. It's always good to backup.

If one drive fails the data is lost. Same as in Raid-0.

Don't know anything about the parity though.

My next move is to restore my system to a Raid-0.

I know that stripping data across fusion drive is intended for disk drives, it most likely has some intelligence built in the code that may slow down the speed. Pure, straight, even stripping can be faster.

Now that I know that two SSDs in a fusion drive are faster, it can only get faster.

Cheers.

Reply

Merge 2 SSDs into a fusion drive (Core Storage)

Similar questions