Best filesystem configuration for hard drives of multiple sizes

**ttshivers** · April 18th, 2012

I was just wondering what the best file system and configuration for an array I want to build. I have 2 (2 TB) hard drives and 2 (500 gb) hard drives. I would like to have the most storage space available but also 1 level of redundancy. I would like to have 2 copies of a file on two different drives. This configuration would allow me 2.5 TB of usable storage space. Would a mirrored btrfs configuration be the best or is there another option?

**sj1410** · April 18th, 2012

RAID1 is the only option if you need redundancy. If you could add 1 500GB and 1 2TB harddisk, than RAID5 would have give you redundancy, with performance and more available space (5TB).

btrfs is evolving but not stable yet, I still prefer ext4.

for creating raid refer to

http://www.techpage3.com/2011/01/sim...id5-under.html

**strask** · April 18th, 2012

Originally Posted by sj1410

RAID0 is the only option if you need redundancy.

You mean RAID1.

**sj1410** · April 18th, 2012

yeah RAID1 is mirroring.

**dcstar** · April 18th, 2012

Originally Posted by strask

You mean RAID1.

Yep, RAID 0 is the exact opposite of "Redundancy", it is totally evil and does not deserve to have a "RAID" designation.

With Striping ("RAID 0") you double the statistical chances of drive failure and you lose all your data if one drive of the pair fails.

**ttshivers** · April 18th, 2012

Actually, RAID5 with your proposed additional drives would only give me 2.5TB of usable space, since RAID5 usable space can be modeled by this equation:

(n-1) *s
where n is the number of drives and s is the smallest drive in the array.
In my case this is what happens since I have a 500GB drive.
(6-1)*500GB = 2500GB or 2.5 TB

I want to be able to use the available disks I have and not buy any others.

I am looking for a way to create a redundant disk pool which can accommodate multiple drive sizes. Now from what I understand about btrfs mirroring, it makes sure that a file is present on 2 separate disks in the array, which is probably the best solution for me. Since it would half my total array size and give me a total array size of 2.5TB. Is there a better and more stable way of doing this, since btrfs is still experimental?

**sj1410** · April 19th, 2012

2TB x (3-1) = 4TB Usable space
500GB x (3-1) = 1TB Usable Space

Total 5TB Usable Space

**ttshivers** · April 21st, 2012

This would create 2 different volumes unless you suggest combing them with something with lvm.

**Ceiber Boy** · April 21st, 2012

Originally Posted by dcstar

Yep, RAID 0 is the exact opposite of "Redundancy", it is totally evil and does not deserve to have a "RAID" designation.

With Striping ("RAID 0") you double the statistical chances of drive failure and you lose all your data if one drive of the pair fails.

Yep, but its FAST! as long as you understand the risk and are willing to except the consequences RAID0 is fine! I always (if allowed by my employers) configure my work machines as RAID0 for the performance benefits, in that cerario we have an extensive backup strategy negating the risk of the configuration.

**jmate24** · June 22nd, 2012

yes i personally would go with lvm in that senario but to remember to put a separate /boot partition at the front of the first drive or you will be unable to boot and if you have a usb hard drive then I would suggest using it with deja-dup. Or ordering online backup with http://one.ubuntu.com and deja-dup can backup to the web.

best of luck.