Size printed on the drive label. Different sizes? The array uses the smallest one for every drive.
Advanced settings
Typical hard drive: 100–200 MB/s with no other load. SSD: 400 MB/s or more.
From the drive datasheet. It is a worst-case spec, so real drives usually do better.
Drives that can fail
Rebuild of one drive
Read error during rebuild
Checks for this setup
The same drives in every RAID level
2 drives of 4 TB each.
RAID 0 at a glance
| Minimum drives | 2 |
|---|---|
| Usable space | drives × size of the smallest drive |
| Drives that can fail | None |
| Read and write speed | Up to the sum of all drives for large files |
| Rebuild | Not possible. Restore from backup. |
Common RAID 0 setups
Usable space for each number and size of drives. Every cell opens a page with the full numbers for that setup.
How RAID 0 works
RAID 0 cuts data into small chunks, usually 64 KB to 512 KB, and writes them to the drives in turn: chunk 1 to drive 1, chunk 2 to drive 2, and so on. This is called striping. Because every drive works on its own part of the file at the same time, large reads and writes get faster with every drive you add.
There is no copy and no parity. Each file is spread over every drive, so a single failed drive leaves a hole in almost every file on the array.
If you mix sizes, the array uses the smallest drive's size on every drive. Two drives of 4 TB and 8 TB give 8 TB, not 12 TB.
Every drive you add makes failure more likely
With one drive, you lose your data if that drive fails. With four drives in RAID 0, you lose everything if any of the four fails. The risk adds up.
| RAID 0 of | Chance of losing it in 1 year | In 3 years |
|---|---|---|
| 1 drive | 1.5% | 4.4% |
| 2 drives | 3% | 8.7% |
| 3 drives | 4.4% | 13% |
| 4 drives | 5.9% | 17% |
| 6 drives | 8.7% | 24% |
| 8 drives | 11% | 30% |
The table uses a 1.5% annual failure rate per drive, which is typical for hard drives in their first years. Use the drive failure probability calculator to try your own numbers.
How much faster is RAID 0?
For large files (video, disk images, game installs) speed grows almost in line with the number of drives: two hard drives at 250 MB/s each give close to 500 MB/s. Small random reads and writes, which is what an operating system mostly does, gain much less.
With SSDs, the gain is often smaller than expected. One NVMe drive is already faster than the SATA link of two SATA SSDs in RAID 0, and two NVMe drives in RAID 0 often hit limits in the chipset or the CPU lanes before they double.
When RAID 0 makes sense
- Scratch space for video editing or rendering, where the source files live somewhere else.
- A game library you can download again.
- Caches and temporary files.
Never keep the only copy of anything on RAID 0. If you need speed and safety, look at RAID 10.
RAID 0 vs JBOD (spanning)
JBOD or a spanned volume also joins drives into one, but it fills them one after another instead of striping. You can use drives of different sizes in full, it is not faster, and when one drive fails you usually keep the files that sat only on the other drives. RAID 0 is faster, but a failure takes everything.
Questions
Can data be recovered from a failed RAID 0?
Only if the failed drive itself can be repaired or cloned by a data recovery service. Without it, every file larger than one chunk is missing pieces.
Does RAID 0 double the speed?
For large sequential files, nearly. For small random reads and writes, the gain is much smaller.
Can I mix drive sizes in RAID 0?
Yes, but every drive counts as the smallest one. JBOD or spanning can use the full size of each drive.
How many drives can fail in RAID 0?
None. One failed drive loses the whole array.