disk0 or disk1

tiger1050 · Feb 8, 2013

Hi, new member here (been lurking a lot though) with my first question.

I have a new late 2012 Mac mini i5 and I fitted a OCZ Agility 3 120 Gb SSD, using the OWC fitting kit. The factory fitted 500Gb HDD was attached to disk0 sata connector & the SSD to disk1 sata connector. When I used diskutil to create a fusion drive I chose /dev/disk0 /dev/disk1, which, I think means the fusion is using the HDD (disk0) as the o/s install disk and not the faster SSD.

Am I right in thinking this???

Should I do it again in diskutil but as /dev/disk1 & /dev/disk0 ???

Sorry for the long winded question but I want to get it right.

regards all.

donlab · Feb 8, 2013

tiger1050 said:
Hi, new member here (been lurking a lot though) with my first question.

I have a new late 2012 Mac mini i5 and I fitted a OCZ Agility 3 120 Gb SSD, using the OWC fitting kit. The factory fitted 500Gb HDD was attached to disk0 sata connector & the SSD to disk1 sata connector. When I used diskutil to create a fusion drive I chose /dev/disk0 /dev/disk1, which, I think means the fusion is using the HDD (disk0) as the o/s install disk and not the faster SSD.

Am I right in thinking this???

Should I do it again in diskutil but as /dev/disk1 & /dev/disk0 ???

Sorry for the long winded question but I want to get it right.

regards all.

Setup is fine. You are creating a volume group with those physical disks inside it. You have now created a virtual disk pool that is presented to the OS. You should now see a 3rd disk named Macintosh HD. Now install OS X to Macintosh HD or whatever you named the "drive" but is really a VG.

xlii · Feb 9, 2013

I followed the instructions here and it worked just fine. That was back in November and it's hasn't given me one problem.

http://www.macworld.com/article/2014011/how-to-make-your-own-fusion-drive.html

tiger1050 · Feb 9, 2013

Thanks for the replies, I have already created the Fusion drive with the HDD on /dev/disk0 & SSD on /dev/disk1, however I still don't think things are as fast as they should be using the SSD/HDD drives.

I have looked on the forums/web sites/interweb and have found nothing to say the SSD should be on disk0 & HDD should be on disk1 OR that the fusion creating software KNOWS and puts the SSD as the boot dive ahead of the HDD.

If anyone has more knowledge or info on this,PLEASE post.

Regards all

leman · Feb 9, 2013

The CoreStorage is smart enough to determine which disk is faster and use it appropriately. And disk0/disk1 etc. ids are only labels which can change when you reboot the machine.

Anyway, you can use the iostat terminal utility to monitor the access to the physical disks. Try for instance iostat -d -w 1

donlab · Feb 9, 2013

tiger1050 said:
Thanks for the replies, I have already created the Fusion drive with the HDD on /dev/disk0 & SSD on /dev/disk1, however I still don't think things are as fast as they should be using the SSD/HDD drives.

I have looked on the forums/web sites/interweb and have found nothing to say the SSD should be on disk0 & HDD should be on disk1 OR that the fusion creating software KNOWS and puts the SSD as the boot dive ahead of the HDD.

If anyone has more knowledge or info on this,PLEASE post.

Regards all

Good as it gets. Enjoy your fusion drive.

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