Apple OS X Forum
Raid-0 funny business
Raid-0 funny business
by Rob Viscardis on Jun 7, 2018 at 3:05:16 pm

I've just set up a RAID-0 with 3 internal 6TB 7200rpm drives on my mac pro. Never done a RAID-0 before. I was expecting the total capacity to be the size of a single drive- 6TB. But now that the raid is created, it is telling me the capacity is 18TB. Copying data to the raid doesn't seem to triple the amount of used data. That doesn't seem right to me? Did I do something wrong? I tested the speed and I am getting the appropriate speeds...

I'm on Sierra on a Mac Pro 2009, flashed to 5,1.

Thanks in advance


Re: Raid-0 funny business
by Jared Ewing on Jun 7, 2018 at 5:29:25 pm

That's expected behavior. RAID 0 is stripped allowing for better performance but no redundancy. The link below goes into more detail.

Striped (RAID 0) set: A striped RAID set can speed up access to your data. You can’t create a RAID set on your startup disk; you must first start up your computer from another disk.

https://support.apple.com/guide/disk-utility/create-a-disk-set-dskua23150fd/mac


Re: Raid-0 funny business
by Rob Viscardis on Jun 7, 2018 at 5:54:26 pm

Awesome. Here I was expecting much less storage on the RAID, so I'm pretty happy about that.

Thanks


Re: Raid-0 funny business
by Jared Ewing on Jun 7, 2018 at 6:05:13 pm

You're welcome. Remember that RAID 0 is great for performance but if one of the drives fails, all data on the RAID is lost. Take the time to make a backup elsewhere, just in case.


Re: Raid-0 funny business
by John Rofrano on Jun 8, 2018 at 12:15:01 pm

What Jared Is pointing out is really important. Why did you create a RAID? If it was to protect your data and get redundancy you failed. RAID 0 actually makes your data less secure because if anyone drive fails you will lose all the data on all three drives.

If you were expecting data redundancy you should’ve created a RAID 1 and that would’ve been the size of a single drive and your data would be stored on both drives so that it one drive fails you still have your data on the other Drive. It sounds like that’s what you were expecting but not what you got.

With 3 drives you could also create a RAID 5 to get more space and still have redundancy. So it’s important understand why you created the RAID in the first place to make sure you got what you think you got.

~jr

www.johnrofrano.com
www.vasstsoftware.com


Re: Raid-0 funny business
by Rob Viscardis on Jun 8, 2018 at 1:54:37 pm

Yes, totally important for that to be said. I created the raid for performance, and all my redundancies are in place with externals, so I'm not worried about that. I simply misunderstood that a Raid-0 uses the full amount of space. I thought I would be sacrificing the space for the performance, based on how I'd seen a Raid-0 described, but as it turns out, I get both. So it turns out there's no funny business, and I'm happy.

For anyone that's interested, I'm getting speeds of 550MB/s on the raid.

Thanks guys!





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