Is RAID-0 better than RAID-1?

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Is RAID 0 better than RAID 1?

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:+1: Welcome to Manjaro! :+1:

TL;DR

NO! RAID-0 is worse than no RAID at all!

The long version:

  • To understand RAID levels you need to know about MTBF first:
    • The Mean Ttime Between Failure or any disk can be found by searching the web with keywords brandname modelname MTBF
    • E.G. For the Samsung 860 SSD the MTBF is 2 Million hours (2 Mh) and was devised from the link to Technical Specifications (PDF file) and will be used to calculate the MTBF of the different RAID solutions below.
  • RAID-0
    • a RAID-0 is also known as a stripe and consists of at least 2 storage mediums, which means that if you write a file consisting of 4 blocks, 2 blocks will be written simultaneously on both drives and then another 2 blocks simultaneously again if they’re on separate controllers
    • If one of the disks in a RAID-0 fails, the entire RAID-0 is completely lost.
    • The MTBF of a RAID-0 consisting of 2 Samsung 860 SSDs is effectively half of the MTBF of a single disk = 1 Mh so RAID-0 is worse than no RAID at all!
    • This becomes worse the more disks you add and if you would have a RAID-0 of just 8 disks, the MTBF would have gone down to 250Kh (1/8th of the original MTBF)
  • RAID-1
    • RAID-1 is also known as a Mirror and with the same 4-block file will write 1 block to the first disk, and then the same block again to the second disk and then the second block to the first disk and to the second disk etc until all 4 blocks are saved.
    • The MTBF of a RAID-1 solution is double that of no RAID at all: if one of the disks fails, you replace it and the mirror will be rebuilt and no data is lost.
  • RAID-5
    • RAID-5 consists ideally of 5 disks and uses block-level striping with parity distributed among all the drives.
    • The MTBF of this solution is also double of that of a single drive, but allows much more information to be stored compared to a RAID-1
  • a more in-depth description of the above and other RAID levels can be found here.

Why do people still use RAID-0 if it’s so bad???

That’s an easy one: RAW SPEED, but nowadays RAID-0 is only used in computer clusters where the redundancy is at the computer level and not the disk level: If one of the RAID-0s in a cluster goes down, all the other computers in the cluster just take over the workload while the failed RAID-0 is being replaced.

On a single computer however, RAID-0 doesn’t make any sense because of the unreliability it introduces, except in very specific use cases

:+1:

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Well, every RAID type has it’s purpose. RAID 0 and 1 have different purposes. It’s not that one is better or worse than the other.

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That is true! and:

:man_shrugging:

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AFAIK RAID-0 is/was used by people that needs disk speed, but not necessarily security for the data. For example, video editing is usually used as example of fair use for RAID-0. You may have the raw files in some other disk and must have backups in place. But just for editing and rendering you use the RAID-0.

So even in a single computer it can have some meaning

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Yes, that would be a valid use-case for people who know what they are doing (I.E. mount /tmp on a RAID-0 and copy scratch files there) but for 99% of the people out there, it’s a disaster waiting to happen, but I’ve bowed to your wisdom and put a disclaimer in my original answer and linked to your answer.

:bowing_man:

cc @maycne.sonahoz :point_up_2: :wink:

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Is RAID 0 better than RAID 1?

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You’ve asked this 13h ago and received a reply 13h ago. Why do you insist on asking this again?

:thinking:

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Well @Fabby, I don’t know 'bout OP, but I thank you for a very thorough and clear explanation.

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This thread is general discussion. Information about RAID technology is widely available on the Internet.