why does Linus like raid 5?

seagate_surfer · January 26, 2018

9 hours ago, Damascus said:

I actually only have 2 drives right now, an oem samsung nvme (960gb) and a 7200rpm 2tb barracuda.

I'm trying to find a method to have some sort of backup that copies my ssd to and hdd and then updates it daily/weekly so if the ssd croaks I don't lose everything

If your primary goal is to have a backup, then RAID probably is not the first place you should be looking. RAID is not in-and-of itself, a backup. RAID is for providing redundancy. Like if you have a server managing sales transactions on a website, a hard drive crashes, you have to take the system down to fix the issue/replace the drive and get things back up, that downtime equals lost revenue. Time is money. So instead, you have a RAID, a drive goes down, you don't have to knock your server down, you just replace the drive, the array keeps right on pumping away with no downtime and rebuilds to utilize the new drive. That's the type of scenario that RAID helps with.

The best way to protect/backup your data is known widely as the 3-2-1 method. Keep 3 copies of your data, on 2 different mediums, and 1 offsite in case of disaster. This isn't to say that RAID couldn't potentially be part of your backup solution, you could have a NAS with RAID which backs up to a large external USB drive/multiple USB drives that you then store somewhere other than your home, it just means that on it's own, RAID is not meant to be a backup. So as far as your backups go, if you do end up implementing some kind of RAID somewhere in your strategy, then our solution would be IronWolf drives which are engineered specifically for RAID use. You could also just look into the Backup Plus and Expansion lines if you're more interested in going the route of external USB drives.

ARikozuM · January 26, 2018

@Damascus I would look into Robocopy scripts. Easy to learn, easy to modify, and they can be portable if you’re targeting the same directories or full drives.

Jtalk4456 · January 27, 2018

I've not set up raid before, though I plan to in a future build. The inate dislike of raid 5 is puzzling to me. I looked into the raid options and 5 seems like one of the best choices. Can someone explain why everyone seems to hate on raid 5

And while were at it, can you explain unraid to me vs normal raid, if there is a difference, i'm new to raid in general

ghost001985 · January 27, 2018

14 hours ago, Jtalk4456 said:

I've not set up raid before, though I plan to in a future build. The inate dislike of raid 5 is puzzling to me. I looked into the raid options and 5 seems like one of the best choices. Can someone explain why everyone seems to hate on raid 5

And while were at it, can you explain unraid to me vs normal raid, if there is a difference, i'm new to raid in general

the rating for most drive errors is about 1 in 13000000000000, give or take. which is becoming 1 drive. so if you run a raid 5 and 1 drive fails, you replace that drive, and while rebuilding a bit error happens it will corrupt that raid. say you have 10 by 10tb raid 5, the chance of an error becomes 1 in 8.

but like i have said before, this is only an issue when the drives are 8,10,12 tbs.

not to said raid 5 is bad in small low TB arrays. a 5 by 2tb would be completely fine.

Jtalk4456 · January 27, 2018

2 hours ago, ghost001985 said:

the rating for most drive errors is about 1 in 13000000000000, give or take. which is becoming 1 drive. so if you run a raid 5 and 1 drive fails, you replace that drive, and while rebuilding a bit error happens it will corrupt that raid. say you have 10 by 10tb raid 5, the chance of an error becomes 1 in 8.

but like i have said before, this is only an issue when the drives are 8,10,12 tbs.

not to said raid 5 is bad in small low TB arrays. a 5 by 2tb would be completely fine.

not sure i get the probabilities there, but i'm planning on a 3*2tb raid 5 array, nothing gigantic. So given what you said i should be fine

Since you seem to know about this let me ask you one more thing. I know with raid 1 or 10 you're effectively losing half of your usable space in the array, what is a rough percentage of what i lose in raid 5, i don't know how much the parity data takes up vs the actual data