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RAID 1 setup: Using one HDD for mirroring multiple HDDs

L

Lombardo_Ciccone

macrumors newbie
Original poster
Apr 15, 2024
7
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Good day!

I am trying to mirror via RAID 1, two or more HDDs with one HDD. Is it possible? I would imagine partitioning would do the trick, but I don't see a way to do this when setting up RAID 1 in Disk Utility.
Am wrong, or am I missing a step?

Thanks for advice, folks.
 
Sorry, I didn't understand your first post. After you create the RAID, it should appear to the system as a normal drive. You ought to be able to partition it like normal.

Though you didn't say, are you going to format it using APFS? If so, separate the data using volumes, not partitions. Volumes keep data logically separated but they share the space.

That said, be sure to backup this data. RAID 1 can help save from an individual disk failure, but there are other ways to lose data.

Why is raid 1 not a substitute for a backup

why is raid 1 not a substitute for a backup???
forums.tomshardware.com forums.tomshardware.com

betterstack.com

Why isn’t RAID a backup | Better Stack Community

Ship higher-quality software faster. Be the hero of your engineering teams.
betterstack.com betterstack.com
 
chabig said:
Sorry, I didn't understand your first post. After you create the RAID, it should appear to the system as a normal drive. You ought to be able to partition it like normal.

Though you didn't say, are you going to format it using APFS? If so, separate the data using volumes, not partitions. Volumes keep data logically separated but they share the space.

That said, be sure to backup this data. RAID 1 can help save from an individual disk failure, but there are other ways to lose data.

Why is raid 1 not a substitute for a backup

why is raid 1 not a substitute for a backup???
forums.tomshardware.com forums.tomshardware.com

betterstack.com

Why isn’t RAID a backup | Better Stack Community

Ship higher-quality software faster. Be the hero of your engineering teams.
betterstack.com betterstack.com
Click to expand...
Hi there.
Ah, Ok so I can partition it, but how do I specify which Volume (so yes, APFS file system) points to (mirrors) each HDD? That's what I have to do. Your help is being appreciated as we speak, since the link shows me how to set up the RAID 1.
I am manually (copy, paste) onto a spare HDD now, before setting up RAID 1.

However, the two links you provide are giving me food for thought.
Maybe I need to purchase Super Duper.
 
Lombardo_Ciccone said:
how do I specify which Volume (so yes, APFS file system) points to (mirrors) each HDD?
Click to expand...
I'm not sure what you are trying to do. You'll need two blank hard drives to set up the RAID. Then you can create as many volumes as you wish on that RAID. Is it your plan to create two volumes, and copy one existing hard drive to each volume? (I'm not even sure I put that question into words very clearly)
 
chabig said:
I'm not sure what you are trying to do. You'll need two blank hard drives to set up the RAID. Then you can create as many volumes as you wish on that RAID. Is it your plan to create two volumes, and copy one existing hard drive to each volume? (I'm not even sure I put that question into words very clearly)
Click to expand...
Hi there.

I have 2 external HDDs on a dock, and a RAID 1 HDD on another duck. All connected by USB 3.0 on iMac. (APFS for all HDDS).
I want the RAID 1 to mirror whatever work, or addition of files, that occurs on the first 2 external HDDS.
So, does this mean, I need to create operate volumes for each of the first 2 HDDs?
That's what I need to do.
 
Lombardo_Ciccone said:
I am trying to mirror via RAID 1, two or more HDDs with one HDD.
Click to expand...

If this is for backups what is your plan for the other 2 in the recommended 3-2-1 backup strategy?

Once setup there are a number of programs which can do the synchronizing: Chronosync, Carbon Copy Cloner (on demand only), ...
 
HDFan said:
If this is for backups what is your plan for the other 2 in the recommended 3-2-1 backup strategy?

Once setup there are a number of programs which can do the synchronizing: Chronosync, Carbon Copy Cloner (on demand only), ...
Click to expand...
I've heard of Chronosync, bought CCC 10 years ago, but I have to pay for a new version since my old serial won't work. RAID 1 is free, so I need to try that. Ill look into Chronosync.
I have Time Machine as. backup, and I am subscibed to Carbonite. So 2 local backups (Time Machine and RAID 1) and 1 offsite backup in the cloud.
 
Lombardo_Ciccone said:
Ah, Ok so I can partition it, but how do I specify which Volume (so yes, APFS file system) points to (mirrors) each HDD? That's what I have to do. Your help is being appreciated as we speak, since the link shows me how to set up the RAID 1.
I am manually (copy, paste) onto a spare HDD now, before setting up RAID 1.
Click to expand...
I don’t think that is what you should be doing. I don’t think that is even possible. Why not get another drive and make 2 raid 1 setups
 
NC12 said:
I don’t think that is what you should be doing. I don’t think that is even possible. Why not get another drive and make 2 raid 1 setups
Click to expand...
I see. Maybe I should just splurge on a new HDD. I'm trying to save money. But I'f I cannot have the RAID 1 drive mirror 2 HDDs, then I have to abandon this plan.
 
You need a RAID enclosure to have RAID drives. Some use hardware, some use software, but there’s a distinct difference between mirrored drives and duplicating drives. I’m confused as to
1. What your actual setup is (no such thing as a single drive RAID, it’s a single array)
2. What you want to do… backup a disk? Have an array that has redundancies to allow for failure tolerance? Something else?

Personally I have a NAS in RAID 5, which is a networked 4 disk array. I back up my computers on that (GOOD) but I also use it as a streaming server without further backup (NOT GOOD)…
 
Last edited:
I think it'd be best to abandon this plan, as it isn't really the best way to set up a RAID. It might be possible, but you'll be losing a lot of the benefits by bottlenecking the I/O with 1 drive shared among the two separate RAIDs. It's typically considered best practice to purchase multiple drives of the same type and capacity and RAID them together from the start. I've done some odd things like shucking older HDs and popping them in an enclosure together as a RAID 1 setup but that's just for data I don't care about too much. I don't trust my more important data to anything less than my RAID 5 with backups.
 
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