RAID 1 ?

[Benliam12]

I'm planning on buying a new Hard Drive to I can backup my stuff & be save with it. So here my situation

 

I already have a computer using a single HardDrive (1TB) and I want to get 2 new Drives & run all of them in Raid 1 (So all of them are identical) Now I want to know if first I can do Raid 1. Do I need to check any thing before buying these new drives. Can I install the Raid 1 even if my first disk is already half full ? It is at first possible to run 3 disks in Raid 1 ? Finally, can I un plug one of the 2 new drives (not the bootable one), take it home and plug it back in a week and still be synchronized with the 2 left in the computer ? 

 

Also, does any body knows how to setup a Raid 1 & want to give me a steps list on how to setup one ? 

 

For any more infos please be free to ask.

[swordsman247]

For a raid array they have to be the same model/size and always hooked up at the same time when the computer is on. To use an existing drive it would need to be wiped. I think a 3 disk array would be a raid 5? Not sure as they're not a very common setup. Here are some vids that should fill in the basics.

 

[Benliam12]

But like I cant like tell the disk I already have to be copied on the 2 others  ?

[pwn_intended]

1 minute ago, swordsman247 said:

For a raid array they have to be the same model/size and always hooked up at the same time when the computer is on. To use an existing drive it would need to be wiped. I think a 3 disk array would be a raid 5? Not sure as they're not a very common setup. Here are some vids that should fill in the basics.

 

Not true. Intel's RAID software will handle drives of different make/size no problem, it will just reduce the amount of space available to whatever the smallest drive is.

You can make a 3 disk (or however many you want) RAID 0. Adding more drives does not change the RAID level, but 3 is the minimum number of drives for a RAID 5.

The part about wiping the drives is true though, as I believe that they have to be initialized together with the intel raid software, which has to be enabled in your BIOS.

 

As far as the swapping of the drive between multiple machines, it may work but it is definitely not what RAID is designed for and I would not recommend doing that.

 

[swordsman247]

Just now, pwn_intended said:

Not true. Intel's RAID software will handle drives of different make/size no problem, it will just reduce the amount of space available to whatever the smallest drive is.

You can make a 3 disk (or however many you want) RAID 0. Adding more drives does not change the RAID level, but 3 is the minimum number of drives for a RAID 5.

The part about wiping the drives is true though, as I believe that they have to be initialized together with the intel raid software, which has to be enabled in your BIOS.

 

As far as the swapping of the drive between multiple machines, it may work but it is definitely not what RAID is designed for and I would not recommend doing that.

 

Ah I always forget you can build them in software now...oh how times have changed.

[Ziggy114]

I know it's possible with Linux software RAID to create a RAID 1 mirror out of a disk that already has data and a new, blank disk without losing anything - basically the idea is that you create a degraded RAID 1 array with the new, blank disk (degraded meaning the array is aware there should be a second disk, but it's not been added yet), move the data from your existing disk onto that degraded array, then wipe the original disk, add it to the array and allow the data to be mirrored. I don't know if this is possible with other hardware / software RAID solutions, but you would think that as long as your controller of choice allows you to create a degraded mirror with one drive and write data to it, then this should be possible. Google is your friend!

 

Ideally, any redundant array should always use identical drives. Depending on the controller / software you can use different drives, even ones of different capacities, but it's better to avoid doing this if you can.

 

Concerning the different RAID types, be careful:

• RAID 0 is a striped array and is meant to pool storage and increase performance (2x2TB = 4TB usable), but offers no failure tolerance - lose any 1 drive in a RAID 0 array and you lose everything.
• RAID 1 is a mirrored array, which must have at least 2 disks but can have more than that for additional redundancy (depending on what your software / hardware supports). If you have 3 2TB disks in RAID 1, you'll only have 2TB worth of usable space but can suffer up to 2 drive failures without losing any data. As long as one disk survives, your data does too.
• RAID 5 uses single-drive parity - basically one drive worth of space is used to store "parity" data, which can be used to reconstruct the data on a drive if it fails. You need a minimum of 3 disks for this and usable storage will be roughly the number of drives less one times drive capacity (3x2TB = ~4TB usable, 5x2TB = ~8TB usable, etc), and it will be tolerant of a single drive failure. If you lose a second disk before the failed drive is replaced and the data reconstructed, you lose everything.
• RAID 6 uses two-drive parity - same idea as RAID 5, but can suffer up to two drive failures before data is lost - lose a third before/during replacement or before data reconstruction finishes, everything's gone. Requires an absolute minimum of 4 disks, but practically speaking (because of RAID 10, which I'll describe below) it doesn't make much sense to use RAID 6 with less than 5 drives. Usable space under RAID 6 would look something like this - 4x2TB = 4TB usable, 5x2TB = 6TB usable, 8x2TB = 12TB usable, etc.
• RAID 10 is made up of two or more RAID 1 arrays that have been combined in a RAID 0, and is the reason RAID 6 with less than 5 drives doesn't make sense. Basically as long as one of the drives survive in each of the constituent RAID 1 arrays you don't lose any data, but if one of the RAID 1's loses its final drive and fails, everything's gone. In this respect with 4 drives its fault tolerance is slightly worse than RAID 6 as RAID 6 can lose any 2 drives instead of only 1 drive from each underlying 2-disk RAID 1 array in RAID 10, but the processing overhead for RAID 10 is a lot lower and the performance tends to be a lot better, especially on writes.

RAID 5 and 6 look appealing in that they offer fault tolerance without sacrificing 50% or more of your raw storage space, but they have their drawbacks - your RAID controller (or computer in the case of software RAID) has to work a lot harder when writing data to disk, as it has to do and write all of the parity calculations so that data can be reconstructed if a drive fails. Also, when replacing a failed drive, there is a lot of work that has to be done both by your computer and the surviving drives to reconstruct what was on the failed drive, meaning you're literally putting the surviving drives through the wringer when replacing one that's failed, increasing the likelihood you'll suffer another failure before reconstruction is completed. Anything based on mirrors (RAID 1, RAID 10) is far easier on your computer and on surviving drives after a failure, but has the drawback of maxing out at 50% storage efficiency - you'll never get more than 50% of your raw storage as usable space in a mirrored configuration.

 

This post ended up being a ton longer than I intended when I started writing it, but I hope it's helpful. There's a ton out there on RAID, what it's good for and where it comes up short - for instance it's good to have some internal redundancy, but RAID is not a replacement for a proper backup. Maybe this is more information than you were looking for, but if you're at all concerned with holding on to your files in the long term (maybe some things are irreplaceable), you might want to do some additional reading.

 

Good luck!