RAID options

[LukeNukem9]

So recently I just got a Dell PowerEdge T310 and I plan on using it as a NAS. Right now its configured with 3 250GB OEM drives from dell all connected through the raid card. I plan to slowly add 2TB WD Red drives until I replace all of the dell ones. It can handle up to four drives. What raid would be useful in this case?

[Mira Yurizaki]

It depends on what you want and what you need:

• RAID0. Listing it here anyway for completeness. It has speed, but is obviously not a good choice for any reliability because if one drive goes down, the entire thing goes down.
• RAID1. You can have complete redundancy, but you also lose capacity. At best you can only do whatever the capacity is of two drives by having two RAID1s.
• RAID5. It offers a mix of reliability and more capacity, though write performance is reduced. You can lose at most one drive and while you can still use the RAID array, performance is degraded.
• RAID 1+0 or RAID 0+1. Requires four drives. It's a combination of RAID 0 and RAID 1 (I'm not sure how much order matters). You get the speed of two drives, but also the capacity of two in this case.

[LukeNukem9]

@Mira Yurizaki Thanks! Another question is if i wanted to add a drive, Do i have to recreate the entire raid, destroing my data?

[Mira Yurizaki]

Just now, LukeTheCoder05 said:

@Mira Yurizaki Thanks! Another question is if i wanted to add a drive, Do i have to recreate the entire raid, destroing my data?

I'm getting mixed answers, so I'm going to defer to the answer of look at what your RAID controller/software allows for.

 

However to play it safe, you should assume that data loss is possible and so you should have a backup copy.

[dalekphalm]

1 hour ago, LukeTheCoder05 said:

So recently I just got a Dell PowerEdge T310 and I plan on using it as a NAS. Right now its configured with 3 250GB OEM drives from dell all connected through the raid card. I plan to slowly add 2TB WD Red drives until I replace all of the dell ones. It can handle up to four drives. What raid would be useful in this case?

What RAID Card is being used in that server? I'm assuming it's the H200. If so, the H200 does not allow for expanding an array.

 

You can technically replace a drive with a larger one, rebuild the array, repeat with each new drive, and then after the last drive has been replaced and rebuilt, you can expand the partition. But this process sucks, and takes forever, and risks data loss.

 

If you want to expand the RAID Array with the H200, the ideal way to do it, is backup the data, destroy the old array, put the new drives in, rebuild the array, copy the data back.

 

In terms of using 4 drives in RAID, it depends on whether you want maximum capacity (RAID5) or better performance (RAID10).

 

RAID5 will mean you lose the capacity of one of the 4 HDD's (you get 3/4th of the total capacity). With RAID10, you lose half the drive capacity (1/2 of the total capacity).

 

Example: 4x 3TB = 12TB

RAID5 = 12TB * .75 = 9TB usable space

RAID10 = 12TB / 2 = 6TB usable space

[LukeNukem9]

@dalekphalm Ok, ill probably do a RAID 5 in that case, although on a spec sheet I read, it says that the limit is 10TB. Is that necessarily true?

[dalekphalm]

1 minute ago, LukeTheCoder05 said:

@dalekphalm Ok, ill probably do a RAID 5 in that case, although on a spec sheet I read, it says that the limit is 10TB. Is that necessarily true?

No - they post the maximums based off of the maximum drive size you can buy at the time of publication. It should support larger drives no problem.

[LukeNukem9]

1 minute ago, dalekphalm said:

No - they post the maximums based off of the maximum drive size you can buy at the time of publication. It should support larger drives no problem.

Ok, thanks. I didn't think that was a thing at first, but thanks for helping.

[leadeater]

8 hours ago, LukeTheCoder05 said:

@Mira Yurizaki Thanks! Another question is if i wanted to add a drive, Do i have to recreate the entire raid, destroing my data?

Simple answer is for any RAIDs that use stripes or mirror then no you cannot expand them only replace and extend (as @dalekphalm mentioned), all parity RAIDs can do both. If you mix/nest RAIDs then you can expand only the parity portions.

 

RAID0: No

RAID1: No

RAID5: Yes

RAID6: Yes

RAID10: No

RAID0+1: No

RAID 50: Yes, only the nested RAID5

RAID 51: Yes, only the nested RAID5

RAID 60: Yes, only the nested RAID6

RAID 61: Yes, only the nested RAID6