RAID Test....Failed....

  • Okay, so I thought I'd do a test of the RAID system. I have 6 varying size drives set up for a RAID 6. Fresh OMV install. Operational, everything working as expected.


    RAID 6, supposedly 2 failed drives and it will still work....UNTIL


    I disconnect ONE of the drives from the array. The ARRAY disappears from OMV and is no longer accessible and does not appear under the RAID Management window anymore.


    THIS IS NOT COOL. Unless I am totally misunderstanding what is supposed to happen here.


    This indicates to me that even a single drive failing will bring the array down. So what is the point of having a RAID 6, or 5 for that matter, if this happens?


    Jeff

  • Typcially, it keeps going when a drive fails while it is running. Also, it may not have started but it should be able to be manually assembled with two drives missing from a raid 6 array.


    A raid array should have identical disks. Using disks of different sizes means you only use the space on each drive the size of the smallest drive. Plus, you probably have drives of varying speed. This is just asking for things to go wrong.


    Raid is not backup either. With different size drives, you probably should use the unionfilesystem plugin and backup the data to other drives.

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  • Yes, I am aware about the same size drives and backups, but all that was not the point of the test. It was to insure that there was continuous SERVICE in the event of a hard drive failure which I have proved there is not. Is this a failure of OMV, the operating system, the hardware?


    I should also point out that there are six drives in the RAID 6 configuration, (3) 1TB, a 2TB, a 3TB, and a 4TB. My total available size in the array is 3.64TB. If it only uses the space of the smallest drive on each drive, why is my array not 1TB?


    Jeff

  • It was to insure that there was continuous SERVICE in the event of a hard drive failure which I have proved there is not. Is this a failure of OMV, the operating system, the hardware?

    Are you unplugging the drive while the array is running? Starting a system with two drive missing is not the same as two drives failing while the array is running.


    I am aware about the same size drives and backups, but all that was not the point of the test.

    I understand. I always mention the backup stuff when people are worried about raid problems. I will still say that using non-identical drives has caused issues in the past including the test you are attempting. So, I don't think it is the best simulation of something you want highly available. Also, there are plenty of new "green" drives that are not good for raid arrays. Maybe you are using some of those drives?


    I should also point out that there are six drives in the RAID 6 configuration, (3) 1TB, a 2TB, a 3TB, and a 4TB. My total available size in the array is 3.64TB. If it only uses the space of the smallest drive on each drive, why is my array not 1TB?

    3.64 tb is correct. It uses the space of the smallest drive on EACH drive. If you have six drives in a raid 6 array, then you will have 4 x 1tb. 3.64 is difference between TB and TiB.


    Is this a failure of OMV, the operating system, the hardware?

    It isn't OMV. OMV just configure mdadm software raid. If that doesn't start with missing hardware, that is something going on with mdadm. The OS isn't really the issue as much as the kernel. You are using OMV 2.x which is an aging kernel. New kernels seem to work better. You don't mention what the hardware is. Unless it is server grade hardware, it could be contributing to raid problems especially on boot. If you really need redundancy, I would use a hardware raid controller.

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  • Can I ask why Raid isn't a backup.

    There are a lot of threads here about this topic. The main reason for RAID is data availability if a drive fails. During an rebuild after a disk failure often a second drive fails and then all data has gone in an RAID5 array. So it is strongly recommended to have a backup up one´s sleeve.


    Many users have data on a NAS exclusively which are not on the computer(s) a second time. In the case above this data is lost completely.

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    Edited once, last by cabrio_leo ().

  • Can I ask why Raid isn't a backup.

    There is a very good article here that I suggest you read particularly the section downsides to using raid.


    The real problem is that hardware manufacturers of NAS hardware implement Raid from the get go, likewise 'you tube gurus' even do this on a Pi. The upshot is most home users believe that this is a 'must have' scenario and looking at the original post using mismatched drives can cause issues, likewise pulling a drive from a running software raid to 'simulate' a drive failure also fails and the raid disappears.

  • Can I ask why Raid isn't a backup. For example surly backing up your computer to a nas is better then not and then backing up to a nas in Raid 1, 5, 6 or other ones like this is good as it means you have extra data redundancy. I just curious why you don't think it is though?

    Here's two of the more glaring examples from recent memory... I'm sure Google would turn up many more if I was so inclined. It's a mistake nearly everyone makes (I was fortunate and the loss, while it took me a while, I was able to get everything back.. not happening again).


    https://emby.media/community/i…deleted-all-of-my-movies/


    https://forum.openmediavault.o…system-crashed-RAID-gone/

    Air Conditioners are a lot like PC's... They work great until you open Windows.


    Edited 2 times, last by KM0201 ().

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