RAID1 enclosure for Mac Mini?

Posted on 2015-01-19
Last Modified: 2015-02-07
I have a brand new Mac Mini, we're going to be using it as a server.

I also have 2x Seagate Constellation ES.3 2TB SATA drives, which I would like to put into a RAID1 array for the storage of our files.

What's the best way to get these Seagate Constellations connected to the Mac Mini? Obviously there's no good way to install it internally in the Mac Mini so I'm imagining some sort of Thunderbolt or USB3.0 based enclosure is what I need, but which ones are the most mainstream? And is the RAID implemented in software by the Mac Mini, or in hardware by the enclosure? Which one is the best to get that won't bottleneck the performance, and will be the most well-supported down the road?
Question by:Frosty555
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Assisted Solution

ComputerTechie earned 250 total points
ID: 40560355
We have had good luck with these.

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Expert Comment

by:Aaron Tomosky
ID: 40560578
I use a few of these 2 bay enclosures but they seem to be discontinued
No software, no drivers, I used them as eSATA.

It looks like they have been moved to the MobileRAID line

I'm sure the 4 bays over USB3 work in a similar fashion if you want something bigger
LVL 31

Author Comment

ID: 40573597
What is the relationship between eSATA and Thunderbolt? I know that there are adapters that convert between the two but is this an active conversion that introduces latency/performance issues/weirdness, or does Thunderbolt natively support the eSATA protocol and it's just a passive form factor change like DVI<->HDMI?

Basically, if I'm choosing between native USB 3.0->USB 3.0 communication or eSATA->[adapter]->Thunderbolt communication, which one is preferable?
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LVL 39

Accepted Solution

Aaron Tomosky earned 250 total points
ID: 40573693
USB3 can handle the performance of 2 spinning drives in a raid1 just fine  (usb2 cannot). Technically esata and thunderbolt are faster, but with 2x drives in a raid 1 it doesn't matter.

So to answer your question, if you have a usb3 port, use that. No need to introduce a esata->thunderbolt adaptor.
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Expert Comment

ID: 40574520
What is you reason for using RAID1?  If your sole reason is backup, then RAID, even a RAID1 mirror, by itself is not sufficient backup.

Do you need large storage?  Then use RAID5 with multiple disks.
Do you need uptime?  Then use RAID1 and keep cold spares to swap out failed disks immediately.
Do you need speed?  Then use RAID5 or RAID6 or even RAID3 to fill the SATA3, iSCSI, Fibre Channel busses with multiple aggregate disk access.

Do you need Backup?  Then get a Backup solution.  RAID is not backup unless you're using it as a secondary or tertiary location for data.  You need 2 units, purchased at different times from different vendors to get different batches of disks if you want backup or you might have 2 disks fail within a week or 2 of each other.  In RAID1, both disks are running at the same time with the exact same data and wear characteristics.  If the data doesn't exist elsewhere, you don't have a backup.  If your RAID controller fails, then your entire RAID also fails.  It's not sufficient as backup.

It would be simpler and cheaper to purchase two or even 3 separate and differently branded external drives and copy the data if what you want is backup for a very low end system.  In your case, I suggest 2 external enclosures and run rsnyc and time machine or get backup software depending on your needs.  1 disk should be storage and 1 disk is backup.  Then purchase a replacement in a year or 2 and migrate out one of the older units during the 3rd or 4th year.  Repeat every year or 2 and you'll have a stable copy in triplicate, one of which can be taken off site for long term storage.  That's backup.  That way, you get into the habit of doing a backup.  Your backup disk would have less usage and less wear and tear.  That allows it to be more likely to be functional when your primary storage disk fails.  You'd also get in the habit of verifying the backup and doing a restore and that's actually the most important part of any backup.  2 TB disks are cheap.  There's even the 2.5" portable external 2TB USB3 drives for $80-$100 now.  They're good candidates for your off site backup.

A single 2 disk RAID1 is mostly for bootdisk system uptime and you should have spare disks available to swap in as soon as 1 fails.  People that use these 2 disk RAID1 units as "backup" become complacent and end up losing data because they don't ever do anything with them until they fail.  They then all too frequently do the wrong thing and lose their data.  If you had a RAID1 mirror of a RAID5 or RAID6, that might be somewhat sufficient for primary backup, but you better still have a 2nd backup taken off site.

Sorry for my little rant, but I've dealt with too many small companies that don't understand backup and use these units home RAID units for backup because of marketing and because general consumers don't understand that backups and RAID really solve separate issues.  I'm making an assumption about your reasons for wanting a RAID1 because of my experience and apologize if I'm mistaken.  I know you want storage, but that only requires a single external disk.  People tend to buy these mini RAID1 units because they believe it's also sufficient for backup when it's only partially suited as backup.
LVL 31

Author Closing Comment

ID: 40595994
Ultimately we ended up using a single disk in a USB3 enclosure, and ditching the RAID1 entirely, mostly because I trust these enclosures less than I trust the disks themselves. Thank you for the suggestions and the insight.

serialband - I made zero indication whatsoever in my question that I was looking for a backup solution or that I was intending on mistakenly treating a RAID1 array as a backup, and it's a little irritating to get an unsolicited lecture from you about it. Save it for the posters who actually appear to be conflating the two in their question.

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