Mac Mini Raid setup - Raid 1 - mirroring Hard Drives

"Inspired" by John Stump's HDD crash, got thinking about doing a RAID setup with a Mac Mini since the Mini has provisions for 2 internal HDD'S (or 2 - SSD's) They do need to be identical.

Googled this topic and came up with this among many other listings, Seems like a good idea for reliability.

http://wisebyte.blogspot.com/2014/01/best-configuration-for-mac-mini-server.html

Any issues to consider when using this with Hauptwerk>\

Rgds,
Ed

Researching further:

https://www.lifewire.com/raid-1-mirroring-hard-drives-2260278

Assume the failure rate for any one drive is 10 percent over its expected lifetime. The possibility of both drives in the set failing at the same time would be (10 percent) raised to the power of two (the number of disks in the set). The resulting effective reliability becomes a one percent chance of failure over the expected lifetime. Add a third disk to the RAID 1 mirrored set and the resulting chance of failure drops to .1 percent.

That is pretty significant for a system that "has to keep working such as for a church" As the article states, Raid 1 is not a substitute for a data backup.

Here is further - How To Do It info.

https://www.lifewire.com/use-disk-utility-to-create-a-raid-1-mirror-array-2260917

Looking as to how to be alerted when there would be a drive failure not that the organists would be "driving the organ" with an unknown :flat tire". Ignorance is never bliss - I've learned. Could monitor a log, but it would be neater for the system to lite a red (nag) light somewhere on the console indicating a (Raid 1) drive failure. Maybe even a flashing red LED?

Rgds,
Ed

I heard that is is best not to use two drives from the same manufacturing 'batch' as it somehow affects the statistcs. I'm not sure how you ensure that however...

I've heard many things, mostly very positive. This is an new one. Interesting to find the basis for that idea.

Rgds,
Ed

Here's another interesting read:

https://www.backblaze.com/hard-drive.html

---john.

Don't forget, if you have two drives running at the same time you will have twice
as many drive failures over a given period.

If you run two drives at once you will get twice as much noise from them.

Two drives will take twice the power to run and generate more heat either making them less
reliable or needing more (potentially noisy) fans.

I have been using hard drives ever since they first became available and in that time only
one has failed and that was a great many years ago. Always their lack of capacity has
caused me to 'retire' them for a newer one with more capacity long before there was any
sign of failure.

csw900

Mirroring and other forms of RAID is the normal way IT services ensure that data is kept available. For a public HW system mirroring would be a sensible approach and reduce the risk of the system not being available because of disk failures. The Mirroring system should send alerts to another system which is listening for such events and this should in turn alert the sysadmin about any problems.

When setting up raided / mirrored disk sets, we used disks of the same type but tried to use disks from different batches (determined by the serial number) for the mirror disks. This was to minimise the risks of any increase in the probability from faults iin any particular batch of disks caused during manufacture or with the materials used. Very occasionally a disk manufacturer would alert customers for "problems" with a particular batch of devices and using different batches for the mirror help reduce he risk of such failures.

At work we used both hardware and software mirroring in PC (Windows and Linux) and MAC servers and found this valuable for improving system availability at the cost of some additional hardware and increased complexity. Today both Windows and MacOS have made this simpler and appropriate for home use where higher levels of system availability are needed.

Iain

Assume the failure rate for any one drive is 10 percent over its expected lifetime. The possibility of both drives in the set failing at the same time would be (10 percent) raised to the power of two (the number of disks in the set). The resulting effective reliability becomes a one percent chance of failure over the expected lifetime. Add a third disk to the RAID 1 mirrored set and the resulting chance of failure drops to .1 percent.

Again, https://www.lifewire.com/raid-1-mirroring-hard-drives-2260278

No additional heat generated using SSD's and power consumption is down slightly altho that's insignificant. Reliability is the main concern and focus.

Still looking for a way to monitor if a drive goes belly up. Found out the Mac system automatically (in the background) regenerates data to a replaced drive. You can even use the system (play the organ) while this is taking place. I did find you need to have an external bootable drive due to the need to erase all files (both drives). I have a 8 GB thumb drive (bootable and with the OS installed on it). Press and hold "Option" ( key) when starting up the computer and use the DIsk Utility to erase, etc. When done erasing, press the RAID button (on Disk Utility) and drag over whichever drives you want for RAID system. You need also to give the RAID setup a name. The total useable space is determined by the smallest drive. All data is erased. Whole thing takes just a few minutes (to do). And so far looks good. Of course using SSD's does make for a speedy load. Process is much easier than it used to be.and with Mac OS's (10.9 and higher) no additional software.

Rgds,
Ed

The calculation of the probability of a Raid 1/ mirror failure which results in data loss over a particular period is more complex. It involves the probability of the initial failure, the time taken to replace and rebuild the failed drive and so on. You can find calculators for the probability of data loss with raided disks on the web for example here http://wintelguy.com/raidmttdl.pl.

The calculation of the probability of a Raid 1/ mirror failure which results in data loss over a particular period is more complex. It involves the probability of the initial failure, the time taken to replace and rebuild the failed drive and so on. You can find calculators for the probability of data loss with raided disks on the web for example here http://wintelguy.com/raidmttdl.pl.

I was "told" these probability numbers guys are also part time bean counters and do personal tax returns as well. Just kidding of course. I greatly admire what they do. Without number crunching, we wouldn't have computers.

Speaking of the time to replace a faulty drive in a Mac Mini, somewhere around 20 minutes maybe a little faster. So yeah, that's a factor to consider as well.

Rgds,
Ed

Then there's the story of the guy that planned a trip thru a very isolated, remote jungle. He took every spare part for his vehicle that he could fit in. And, yes he did break down in the worst possible place. But all of his spare parts didn't help because he broke the rear axle from all the extra weight of the spare parts and he didn't have a spare axle.

Wouldn't it be nice (besides being able to have 32 GB of RAM) for a Mac Mini to have a slide in carrier for the drives instead having to do major surgery to add or change one deep in the bowels of that machine?

I seem to recall that in the US Army, soldiers were taught to take apart and clean their rifles in total darkness. I've taken apart (and altered) quite a few computers, including Mac Mini's, but don't think I've reached the skill level to do it in the dark.

Rgds,
Ed

[mdyde]

Wouldn't it be nice (besides being able to have 32 GB of RAM) for a Mac Mini to have a slide in carrier for the drives instead having to do major surgery to add or change one deep in the bowels of that machine?

You can also get external Thunderbolt multi-drive RAID array units with hot-swappable drive caddies.

Thanks, Martin.

I did look at those. Was under the impression that Thunderbolt wasn't fast enough to stream cache files in real time? Kinda on a par with USB 3? If transfer speed wouldn't be an issue, we could consider expanding the capacity of a Mac Mini maybe using an external SSD Thunderbolt drive.

What we need is software that could multiply (compressed) lower speed input and output (expanded) to higher speed. A Zip arrangement of sorts or a speed multiplier. Didn't get much sleep in the last 24 so stuff like that is exported by my brain.

And then the high end computer guys are working with super computers that can deal with 1's (ones) and 0's (zeros) simultaneously in super cold state No doubt I won't see those in my lifetime.

Rgds,
Ed.

Just Google "thunderbolt speed vs usb" and you will get your answer.

csw900

[mdyde]

Hello Ed,

Yes -- Thunderbolt 2 can theoretically transfer 20 GB/s (4x faster than USB 3.0):

http://www.techradar.com/news/computing-components/peripherals/thunderbolt-vs-usb-3-0-vs-esata-931343

... so Thunderbolt definitely wouldn't be a bottleneck for loading organs on current computers, even with the fastest CPUs and an array of the fastest SSDs.