is it wiser to get two 4T instead of one 8T hard drive

not taking the money into consideration, is it wiser to get two 4T HDD instead of one 8T HDD if 8TB is the desired capacity? because it's more likely for one drive to fail than two drives to fail at the same time in terms of probability ?

Am I thinking correctly? Or is there anything I'm missing

 

Actually, there is a lot of thinking on these kind of statistics when dealing with lots of systems, and known vs estimated failure rates.

When you are dealing with a small sample set, like 1 or 2 drives, you really can't effectively guess correctly which is better.

I've tried, and succeeded, and failed - both the reverse of what I expected

2 really "bad" drives, Maxtor's I bought on short notice that turned out to still be fast, cool running, and reliably running many years later.

While the single Seagate drive I bought for an important build, failed but is still running 90% many years later - it's got bad sectors that lop off the top of the 1GB size, but the rest has lasted just fine.

There was a big Seagate scandal from that era about huge numbers of drives failing, but if you dug deeper you could usually save 90% of the drive, partition it, and move on. Most people just trashed them.

You could say that increasing the count from 1 drive to 2 drives increases the probability of failure - you now have 2 potential points of failure instead of 1 - more chances to fail.

Or you could say you halved the likelihood of any 1 drive failing by spreading the risk over 2 drives.

As it turns out, the most important thing is to back up whatever data is important to you in 3 places.

The original place, an onsite backup, and an offsite backup - today that could be considered the Cloud Storage - normally it was just an off-site location that wouldn't go up in flames at the same time as the primary location.

That way if you are backed up adequately, you really don't care what original storage fails - as you can restore it to a replacement quickly (Cloud restore may be very slow).

So maybe spread the $$$ you have over storage you need, and then double it to backup to that 2nd drive - 8TB to 8TB drive - or maybe faster 4x2TB to 2x2TB.

8TB will be a long backup / restore from Cloud, so consider another set of drives off site, tape, or get to know someone with a really fast internet connection from which to do your backups / restores.

I'd forget about HDD's, too slow, get SSD's - I know they are expensive, but your backup / restore is a lot quicker at 500MB/sec instead of 100MB/sec.

 

Simple answer. Doesn't matter. No matter what you do, have a backup solution.

 

@kenny1999 if you're choosing external drives, I'd get 2x 2.5" 4TB drives instead of single 3.5" drive because they are less fragile. Otherwise, just get single 8TB drive.

 

If the entire capacity (8TB) is needed for actual storage of unique data - then a single drive is 'safer', statistically.

But as already mentioned; don't buy a 1MB drive (yeah; no typo...) if you haven't accounted for 3MB or more of additional/multiple storage units as backup for DATA stored on that 'live' 1MB drive.

If you do opt for 2x xTB drives - make sure they're not the same make and models - the probability that they'll fail (almost) simultaneously increases if you buy identical samples.

The idea is simple; for DATA you need indefinitely... if you require XX capacity of storage, then buy/have 4XX capacity available for live use and backup purposes.

If these drives are to be used for replaceable data (i.e. downloaded video, etc. ...) then take into consideration your time to get your setup up to speed in case of failure if/when catastrophe happens.

Don't forget that there are differences between manufacturers and models out there... not all HDD's (just like anything else in life) are comparable for reliability, longevity and if important; performance.

Hope this helps.

 

All hardware fails in due time. Have multiple backups, no matter what setup you choose. But, as mentioned before, budget for 24TB instead of just 8TB.

 

Jarhead; just a slight correction - I suggest 32TB of total storage for important DATA - 8TB for the actual DATA, and 3x 8TB of separate and unique additional storage systems (including, but not limited to; model/make/manufacturer and actual physical storage location...) .

 

Fair enough. I personally follow the idea that most of my data isn't important (most of it is shows/movies/games/etc) and save the third layer of backup (offsite) for the truly important (say, my KeePass file).

Of course, maybe every last byte is important data

 

Yup, that's the key realization that solves the ever growing backup problem, only keep what you need.

Deduping is used in industry to help reduce - duplication of backing up the same stuff over and over.

We as individuals can do the same, through only backing up those folders that contain our single creations. No need to back up duplicates of things we can get back quickly. Junk, so to speak.

It is nice though to have a (bare metal) complete image of a boot drive, that saves so much time recreating the working environment over and over - like from a clean install.

An 8TB drive might only have a few hundred GB of stuff we actually need to save, burning the rest instead of saving it saves a lot of backup storage times 3.

 

Yeah; there is DATA and there is Data and there is data. Not all need to be cared for the same.

 

See here: