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3 partitions on iMac 3Tb Fusion Drive - Best Way ?

F

FUN Elendraug

macrumors newbie
Original poster
Aug 12, 2013
4
0
Switzerland
Hi all,


It's my first post on this forum (so please don't flame me directly :D)

I just got an iMac with 3Tb Fusion Drive and wanted to created following partitions:
  • Partition 1 - 100 Gb "SYSTEM" (expected to be used for SYSTEM (MacOS) and software which is really linked a lot to the SYSTEM, such as Office suit, etc ...)
  • Partition 2 - 2'800 Gb "DATA (expected to be used for all the datas as well as software which is not really linked a lot to the SYSTEM, such as games, etc ...)
  • Partition 3 - 100 Gb "SHARED" (expected to be used to share datas over my home network, as well as "security partition" for any purpose)
This is a partition structure I usually use on Macs as well as PCs and which proved to be effective and fulfil my needs.


Unfortunately, I noticed that it is not possible to have more than 2 partitions with the Disk Utility on a Fusion Drive (I must confess, it's my first fusion drive) :(


I also noticed that some users reached to get 3 partitions playing around with "diskutil" in command line:


My questions:

1) Since I have no experience with Fusion Drives, I was asking myself if my usual structure (3 partitions SYSTEM-DATA-SHARED), would be the best structure and would use the SSD in an optimal way ? And if not, what would be the best structure ?

2) Is it possible to install the SYSTEM (MacOS) in the SSD memory and use the rest of the memory (3 Tb) for DATA and SHARED ? Would it be recommended ?

3) Since I have no data currently on the iMac and very little experience with diskutil, could you please help me:
- to identify the disks (partitions) I can erase
- provide me with some insights on how to best erase them with diskutil
- provide me with some insights on how to best create my 3 partitions with diskutil


Please find in attachment a PrintScreen of actual "diskutil list" command.
- SYSTEM (293.0 GB) and DATA (2.8 TB) are the actual 2 partitions on my 3 TB fusion drive
- I guess that Apple_CoreStorage (121.0 Gb) is the SSD Memory
- I have almost no clue what are the other disks, as well as why SYSTEM and DATA are not on the same disk (disk1 with disk1s1 for SYSTEM and disk1s2 for DATA)


I know that this are pretty much questions for a first post ... but as stated I am really lost with this Fusion Drive which is completely new to me and doesn't react like other drives I used before.


Many thanks in advance for any help :)

Best regards,


FUN
 

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Drives need to be partitioned to allow booting different operating systems off the same drive. In some cases partitioning helps in making backups.

On the other hand, partitioning the drive reduces the effectiveness of the fusion drive to just the first partition, reduces flexibility, and typically is less efficient in disk utilization.

The standard folder structure separates system files from user data files, and even allows user specific programs (in ~/Applications). Any folder can be shared over your lan. For security you can use FileVault II full disk encryption or create encrypted disk images which reside anywhere you wish. The data/programs are logically separate although they will be physically intermingled, but that just a low level system issue and doesn't matter for use.

Basically what I'm saying is don't bother partitioning your drive.
 
Thanks for your replies.

I am confused now: why would people (who seem to be good "technical folks") try to get more than 2 partitions on Fusion Drives if it's that worse and would be that much better to only have 1 partition or 2 partitions (in case of dual-boot) ?

And additionally, isn't having SYSTEM (MacOS) and DATA on the same partition a risk?
I mean imagine something goes wrong with an update or anything else related to the system and system memory ... you would potentially loose all your data (I am not taking into account "external" backups). Having system and data on 2 different partition usually offers the opportunity to reinstall the system in this case and remaining quite sure all data will be fine (since you didn't touched the partition they are on)

FUN
 
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Its because they are "technical" and they think they need to. They brag about it to their internet friends. :)

If your drive dies for whatever reason, its gonna take all the partitions with it. ALL DRIVES FAIL. The sooner you accept that, the easier things will become.

You gotta have a good backup in place. As to your "update" scenario -- anyone who has been burned by a System Software update already knows that you need to BACKUP before applying any such updates. Having both a TimeMachine and bootable backup (using SuperDuper for example) is the only sure way to keep things running smooth. 3TB USB 3 drives are near $100. Worth every penny.

There has never, ever, ever, ever been a risk of having OS X (or 9, 8, 7) and data on the same drive. How do you figure it would be an issue since 99% of all Macs sold in the last 10 years come with a single drive comprised with a single partition?

Some of your links were about bootcamp -- were you planning on installing bootcamp to run Windblows natively? You must update to 10.8.3 for bootcamp to work on a Fusion drive.
 
Hello stumper,


For disk physical failure, I agree with you: there is nothing better than an external backup (timecapsule or whatever).

I was pointing out "logical" failure (updates, etc ...), in which case I found it until yet easier to have a system partition. It was also very useful in the case I wanted to do a "clean" OS reinstallation (in case of a major OS update for example), since I had nothing to do with datas, since they were on a separate partition.

Adding external drives at the ends come to the same than doing a partition ... in less effective regarding speed.

For me, 99% of all Macs (as well as 99% of all PCs) are sold with a single drive with a single partition, NOT because it is the best ... but because it is easier for the manufacturer and also for "not technical" users (for example my parents :D), since they don't understand a lot about computers ...

I don't plan to use bootcamp, since VMware Fusion fulfils my needs regarding other OS.

As stated it is the first time I face "fusion drives", and, since so far all posts tell me not to partition, it seems that for "fusion drives" (and only for fusion drives) it might be better to have only 1 partition, for performance issues ?
(Which is a big change compared how I use to use hard drives "usually")

If no other arguments for partition are posted ... I will do only 1 partition and try to get used to it :cool:


FUN
 
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FUN Elendraug said:
I am confused now: why would people (who seem to be good "technical folks") try to get more than 2 partitions on Fusion Drives if it's that worse and would be that much better to only have 1 partition or 2 partitions (in case of dual-boot)?
Click to expand...

I expect they allow two partitions for bootcamp. I can see multiple partitions for developers. While I just boot alternative OSes off of external drives (so easy on a Mac!) in my Windows life I've had systems with four or more drive partitions to boot different versions of Windows.

And additionally, isn't having SYSTEM (MacOS) and DATA on the same partition a risk?
I mean imagine something goes wrong with an update or anything else related to the system and system memory ... you would potentially loose all your data (I am not taking into account "external" backups). Having system and data on 2 different partition usually offers the opportunity to reinstall the system in this case and remaining quite sure all data will be fine (since you didn't touched the partition they are on)

FUN
Click to expand...

Amazingly enough, with OS X, when you do an OS reinstall, the file system remains intact and the user data is just fine. (This has never been the case when I've had to do a Windows reinstall.) In the case of some sort of partial drive failure you might have a better chance of recovering something (assuming the partition map is intact), but I'd never rely on that. It's what backups are for. And I've found it a bit easier to clone a single partition drive than a multiple partition drive.

I will state here that I do have an (external) data drive that has two partitions, 1.5TB each. But the reason for that is of the two alternating clone backups I make, only one is to a 3TB drive and the other is to a pair of two 1.5TB drives. I couldn't make use of those drives (and "waste not want not") if I hadn't partitioned the 3TB drive.

FUN Elendraug said:
I was pointing out "logical" failure (updates, etc ...), in which case I found it until yet easier to have a system partition. It was also very useful in the case I wanted to do a "clean" OS reinstallation (in case of a major OS update for example), since I had nothing to do with datas, since they were on a separate partition.
Click to expand...

I always do a backup first prior to an OS update, but have never had an issue. I've never had to do a clean install (although I have done them for testing purposes). My user folder has been around since Tiger and I'm now on Mountain Lion (and Mavericks on an external boot drive). Doing noting but upgrades except for one migration.

Several Macs here (we've got 7 at the moment) have had their hard drives fail, but I always restore by cloning a new drive from the backup.

Adding external drives at the ends come to the same than doing a partition ... in less effective regarding speed.
Click to expand...

Huh???

For me, 99% of all Macs (as well as 99% of all PCs) are sold with a single drive with a single partition, NOT because it is the best ... but because it is easier for the manufacturer and also for "not technical" users (for example my parents :D), since they don't understand a lot about computers …
Click to expand...

However you are wrong. 100% of all Macs and some large number of PCs (maybe 100% now as well) do have more than one partition -- a recovery partition. Adding partitions doesn't cost the manufacturer anything since they image all the drives from a single master, and that master can contain any number of partitions.

Sure it's easier for non technical users to only have to deal with one partition, but it's also easier for technical users! Here you have a 3TB drive and have 100GB for the system. Suppose you find out you need 110GB? What do you do now? If you want to repartition the drive you better cross your fingers and pray something doesn't go wrong.

I don't plan to use bootcamp, since VMware Fusion fulfils my needs regarding other OS.
Click to expand...

Parallels here, and I also don't use bootcamp.

As stated it is the first time I face "fusion drives", and, since so far all posts tell me not to partition, it seems that for "fusion drives" (and only for fusion drives) it might be better to have only 1 partition, for performance issues ?
(Which is a big change compared how I use to use hard drives "usually")
Click to expand...

My understanding is that if you have two hard drive partitions, only the first will be "fused" to the SSD, so only it will get the performance boost. But even without the fusion drive having a single partition will give better performance because there is a larger free area which helps in optimal space allocation.
 
Ok, so since in 48 hours nobody has posted anything "for partitioning" a fusion drive, I think that I will give it a try to only have 1 partition ...

=> Thanks to all who have posted ;)


FUN
 
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