Combining Similar Hard Drives to Double the Size. Is it ok?

CerebralFreeze · 10 Jun 2020

Hi, Everyone!I've got a quick question. I read that when you combine two drives in RAID 0 in order to double the size of the drive, the drives have to be "exactly" the same. I wanted to know what "exactly" was defined exactly. (Nice pun, no?) Anyway, I couldn't find an exact meaning. (Ha, I did it again!)I am currently using a Samsung Pro SSD, 512 gig and I am almost all the way full. I was lucky enough to be given a Samsung Evo Plus, 500 gig. Can I use the Samsung Evo Plus and combine it with the Samsung Pro to achieve a 1 TB SSD?Or, are the two models too different?

Would anyone know an exact answer?

Compumind · 10 Jun 2020

Hi.

A RAID 0 can be created with disks of differing sizes, but the storage space added to the array by each disk is limited to the size of the smallest disk.
For example, if a 100 GB disk is striped together with a 350 GB disk, the size of the array will be 200 GB. So everything needs to be exact - in capacity and interface to gain any performance.

Also, using Raid 0 also leaves no data security if that matters to you. You would need to make good backups.

See these resources -

RAID levels 0, 1, 4, 5, 6, 10 explained - Boolean World
RAID 0, RAID 1, RAID 5, RAID 10 Explained with Diagrams

To me, Raid 0 is pointless in a home PC. Use the older Samsung SSD with an enclosure via USB 3.0 as an external drive.
Remember, these are consumer SSD's - there will be constant writing to the other (smaller) drive which will wear it out eventually.

We make parts for IT & A/V professionals that connect, convert, extend, split & switch | StarTech.com

Hope this helps!

hsehestedt · 10 Jun 2020

With RAID 0, data is written evenly across all disks in "stripes". The most efficient use of the space would be to have disks of the same size. If you have disks of different sizes, the system will only be able to utilize the amount of space equal to the smallest disk on each drive. For example, assume you have the following:

Disk 1: 500 GB
Disk 2: 1000GB (1TB)

RAID 0 is limited to using 500GB per drive since the smaller drive is 500GB. Therefore, on the 1TB drive, you would effectivly be tossing away 500GB of space.

Example 2:

Disk 1: 500GB
Disk 2: 510GB

In this case you would only loose 10GB of space on the second drive.

As always, make sure you make good backups. One of the downsides of RAID 0 is that you are increasing the chance of failure. With 2 drives, you double the chance of failure, with 3 drives, you triple the chance, etc. This is because any one drive that fails will cause the whole array to fail. There is no redundancy with RAID 0.

So the short answer is this: If you want to waste, no space, use drives of exactly the same size. Any difference in size is the amount of space you will not be able to use.