General RAID questions

[hat]

I need to expand the storage space in my Plex server. Currently there's a single 1TB drive chugging along. As it would really suck if it blew up, I was considering RAID as a way to guard my shit. I was considering RAID 5 or RAID 6. As I understand, RAID 5 requires 3 drives, and one is "lost" to parity, so if I got three 2TB drives, I'd end up with 4TB, and can stand to lose one disk. RAID 6 is supposedly more reliable, especially with higher capacity drives. It requires 4 drives, and still only one is lost to parity, so 4 2TB drives amounts to 6TB, and can lose one disk.

Some questions.. I know Windows has some RAID capability built in. Can it do RAID 5 or RAID 6? If I change the motherboard, what happens? I know this is a problem with hardware RAID controllers (like if I set up RAID in the BIOS) because different RAID controllers are often incompatible. You can't just move the array... but can you with Windows RAID? Or is Windows RAID a bad idea altogether?

I'm thinking I'll make my main PC (Starlifter, the one with the i5 2400) my Plex server eventually, and retire the current one when I can afford to upgrade. I'll probably hold off on buying the drives until that time comes. At which point, I don't see myself changing the hardware in the Plex server any time soon, so using onboard raid wouldn't be a big inconvenience, if it holds advantages over Windows RAID.

 

[newtekie1]

RAID 6 is supposedly more reliable, especially with higher capacity drives. It requires 4 drives, and still only one is lost to parity, so 4 2TB drives amounts to 6TB, and can lose one disk.

Only half correct. RAID6 requires 4 drives, and 2 are lost to parity. It is more reliable because 2 drives can fail before data is lost, but you lose 2 drives worth of space. So 4 2TB drives would result in 4TB of usable space.

Some questions.. I know Windows has some RAID capability built in. Can it do RAID 5 or RAID 6?

Don't use the Windows built in RAID. They added storage spaces that allows parity, but it is so slow and the parity overhead is terrible compared to a proper RAID.

If I change the motherboard, what happens? I know this is a problem with hardware RAID controllers (like if I set up RAID in the BIOS) because different RAID controllers are often incompatible. You can't just move the array... but can you with Windows RAID? Or is Windows RAID a bad idea altogether?

With Windows storage spaces, nothing really happens as long as you keep running Windows. But hardware RAIDs are not that big of an issue either as long as you stay on the same manufacturer of RAID controller. So, if you use the Intel onboard RAID, you have to keep using Intel based motherboards for the array to work. Same with AMD boards. This is why I recommend getting a PCI-E hardware RAID controller. That way you can just move the PCI-E card to whatever computer you want, hook the drives up, and the array will work.

 

[hat]

I see... so unless you want to use more than 4 discs you may as well use RAID 1. Looks like you lose 2 drives to parity no matter what, so you could have 10 1TB drives and have 8TB.

 

[CrAsHnBuRnXp]

Shameless plug

 

[newtekie1]

I see... so unless you want to use more than 4 discs you may as well use RAID 1. Looks like you lose 2 drives to parity no matter what, so you could have 10 1TB drives and have 8TB.

Basically, the rule of thumb is how ever many drives you can stand to lose without losing data is also the number of drives you sacrifice in space.

So RAID5 can lose one drive and your data is safe, but you lose one drive in usable space. RAID6 can lose two drives and your data is safe, but you lose one drive in usable space.

It is said that RAID6 is safer with larger disk because they take longer to rebuild when a drive fails. If a second drive fails when you are rebuilding the array in a RAID5, then all your data is lost. If a second drive fails in a RAID6 when you are rebuilding, then your data is still safe.

With 2TB drives, I personally don't believe RAID6 is necessary. I'd go with RAID5. RAID1 is really only useful if you are using 2 disks, any more than that and RAID5/6 is better. With RAID5 you can have 3 2TB drives and you'll get 4TB of usable space. To get that with RAID1 you would need 4 2TB drives.

 

[hat]

I read in the event of a disc failure and you need to rebuild the array, raid 5 has met its limit with today's hard drives due to unrecoverable read errors. You can run into one such error when rebuilding the array and then the whole thing goes boom. Raid 6 with 2 parity discs mitigates this issue.

 

[repman244]

Raid 6 with 2 parity discs mitigates this issue.

To an extent yes, if you use the highest capacity drives that are available today you can hit that limit even with RAID 6 due to the complexity of rebuilding.
If you can afford to sacrifice capacity you also have an option of RAID 10.

 

[newtekie1]

I read in the event of a disc failure and you need to rebuild the array, raid 5 has met its limit with today's hard drives due to unrecoverable read errors. You can run into one such error when rebuilding the array and then the whole thing goes boom. Raid 6 with 2 parity discs mitigates this issue.

Using drives designed to run in RAID, like WD RED or Seagate NAS or enterprise drives, also mitigates the issue.

 

[Jetster]

I use FreeNAS. Has been rock solid. Would require a system dedicated to the NAS but what you get is reliability. BTW RAID 5 is not recomemeded anylonger. When you get into drives larger than 1 Tb the rebuild stresses the other drives and the potential to fail is high when rebuilding the RAID. I use RAID 6 with 6 drives

https://www.techpowerup.com/forums/threads/nas-build.240073/

 

[Solaris17]

Just care here, RAID is NOT a backup. So in the event of impending disk failure if data starts getting corrupted before the disk stops functioning (resulting in queue to rebuild) the data could already be bad.

All info in this thread thus far is correct but for those just stepping into the RAID world and understanding it, its important to make this VERY important distinction early on.