Is there a test suite for Pi2/armv7 ?

No, it is not RAID.

I back up once a night. In between if I erase a file its still there on the backup That is not RAID

Ah - it's not a mirror then either it's a backup copy.

Ignoring whether its RAID or not, mirroring will protect you against a random failure of one of the drives, which was more useful in the spinning rust days when random mechanical failures were an issue.

With SSD, write life is the main issue, and if you have two identical mirrored drives, you may find any write life issues, which are not random, occur at exactly the same time.

So with any type of mirrored arrangement, make sure they are different makes or models of drive, so it is less likely they fail together.

---druck

I agree.

But never at exactly the SAME time.

Remember the primary drive gets written to all day long as stuff like this post is downmloaded, read and deleted.

The secondary gets a once a day rsync,

And, whilst I have never had an SSD wear out fromn writes in the past 8 years I have had one fail in a quite different way shortly after purchase.

They are not subject to the same usage pattern, and they are not made from the same components.

As long as they dont fail within 24 hours of each other

s/predicts/tries to predict/. It’s not a prophet, you know.

And it only catches about 30% of failures.

Companies whose business it is to ensure data integrity do not rely on SMART.

No, they use hardware RAID for redundancy, extensive performance monitoring, and retire most disks before they fail based on the small percentage of failures of thousands of other discs of the same type.

But that's not what the typical person with a Raspberry Pi and a couple of discs is able to do. The SMART information gives valuable warning of potential failures, to ignore it would be to employ the STUPID feature of the user.

---druck

Actually, no. They wait until the disks actually fail before replacing them.

Unfortunately, SMART only catches about 30% of potential failures. That’s why relying on it is not smart.

Anyone with any sense would replace them before the bathtub failure curve starts to rise, which is usually not long after the end of the warranty period.

It's smarter than catching 0% of potential failures by waiting until they have already happened.

David

In my previous job, we replaced them when they failed, not before. Customers don't like paying for hardware that will sit there doing nothing.

It entirely depends on usage pattern,. A disk which is being accessed and having huge amounts of data written and erased, yes.

A disk in a desktop computer that loads the OS and does bugger all. Many times longer.

BackBlaze is a company whose business is data integrity. Every 3 months they publish a blog post on the reliability stats of the drives that they use. They don’t replace drives until they fail. Individual failures have essentially zero impact on their business, while replacing drives is a cost.

The problem is being caught by surprise 70% of the time.

This is informative

---druck