I wonder if this would work... criticism and suggestions welcome

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catweazel
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I wonder if this would work... criticism and suggestions welcome

Post by catweazel » Mon Oct 15, 2018 3:35 am

A few years back I created a tutorial on how to install Mint 18 to boot from RAID 0. I went through it recently to see if it still worked on Mint 19. It did, sort of, and not without a lot of pain; the final result was very unsatisfactory. I recently became aware that Ubuntu Server has an alternate installer that supports creating and directly installing to RAID 0, but it's DE-less. It was very simple to then "upgrade" Ubuntu Server to the desired DE, in which case I installed KDE. It's running very nicely indeed, and it's screaming fast on a pair of 3,200Gb/s NVMe drives in RAID 0.

So, that's the background, and here is my idea: Use Ubuntu Server to install Linux Mint 19 to RAID 0. The basic steps would be:

1. Have 3 drives ready. 1 for the initial LM install, and two for the RAID 0, plus a live LM 19 media.

2. Install LM 19 to one drive with a separate boot partition, this is an absolute must. Shut down and disconnect the drive after installation.

3. Run Ubuntu Server and create the RAID 0, then install Ubuntu Server, which creates / on the RAID device and a separate /boot partition that is off-RAID.

4. Shut the machine down and reconnect the disconnected LM 19 drive.

5. Start the LM 19 live media and delete the entire contents of Ubuntu Server's / on the RAID 0 device.

6. rsync the LM 19 / to Ubuntu Server's /

7. Shut down and disconnect the LM 19 drive again.

8. Turn on the machine and enjoy LM 19 in RAID 0.

Before I try this in a VM, do you think I am:
a) missing something, apart from a brain?
b) crazy?
c) wasting my time and yours?

I have reasons for suspecting it will work. Chief amongst those reasons is that LM 19 and Ubuntu Server use the same base kernel. As long as the RAID UUID isn't replaced, the Ubuntu Server /boot partition should mount and start / with LM 19 on it. If you don't think it will work, why do you suppose that is?
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xenopeek
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Re: I wonder if this would work... criticism and suggestions welcome

Post by xenopeek » Mon Oct 15, 2018 4:08 am

I can't imagine what you're doing that needs RAID 0 because your 3,200 GB/s NVMe drives are too slow.

Or that you'd see any significant or even noticeable difference with RAID 0 on such drives except in benchmarks. Real world applications do stuff with the data they are loading and drive speed is just one of the factors for time taken. At some point your drive is faster than your application can make use of. I think you'd have reached that point.

Personally I think you won't earn back the investment in time but hey, if this is something you want to do then go for it. There will be folks with cheap SATA drives that can really benefit from it if you get a new tutorial up.

The Ubuntu installer likely uses mdadm for software RAID? Would it be easier to install Linux Mint 19 directly on RAID if you used LVM RAID instead?
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gm10
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Re: I wonder if this would work... criticism and suggestions welcome

Post by gm10 » Mon Oct 15, 2018 4:09 am

The question is why Ubuntu server worked better for you than LM19. You seem to think it's just about how it set up the partition, in which case you should be able to skip the server install step and just figure out what it does and create your partitions accordingly. My guess would be the package base might also be slightly different though. For example, my LM19 doesn't have mdadm pre-installed, which I would assume is what Ubuntu server uses to set up and run the array.

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catweazel
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Re: I wonder if this would work... criticism and suggestions welcome

Post by catweazel » Mon Oct 15, 2018 4:19 am

xenopeek wrote:
Mon Oct 15, 2018 4:08 am
I can't imagine what you're doing that needs RAID 0 because your 3,200 GB/s NVMe drives are too slow.
I like speed :)
xenopeek wrote: Or that you'd see any significant or even noticeable difference with RAID 0 on such drives except in benchmarks.
Actually, the difference is markedly noticeable.
xenopeek wrote: Real world applications do stuff with the data they are loading and drive speed is just one of the factors for time taken. At some point your drive is faster than your application can make use of. I think you'd have reached that point.
I don't believe that's correct. My RAM can handle around 24GB/s bandwidth and the CPU can feed it. The real reason for installing the software RAID was so that I can compile C++ while watching videos or listening to music as I wait without major hiccups in either video or audio :)
xenopeek wrote: ... There will be folks with cheap SATA drives that can really benefit from it if you get a new tutorial up.
Yes, that's the point of asking here first.
xenopeek wrote: The Ubuntu installer likely uses mdadm for software RAID? Would it be easier to install Linux Mint 19 directly on RAID if you used LVM RAID instead?
Thank you very much for the tip. I wasn't aware of LVM RAID so I'll go and read up.

Cheers.
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catweazel
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Re: I wonder if this would work... criticism and suggestions welcome

Post by catweazel » Mon Oct 15, 2018 4:27 am

gm10 wrote:
Mon Oct 15, 2018 4:09 am
The question is why Ubuntu server worked better for you than LM19. You seem to think it's just about how it set up the partition, in which case you should be able to skip the server install step and just figure out what it does and create your partitions accordingly.
I did that already. It seems tells the kernel what UUID to look for, which is the RAID 0 UUID. I actually suspect that's the only significant difference apart from the need for an off-RAID boot partition. The problem is, getting LM into RAID 0 requires a lot of command line work and it gets complex and the more complex it gets, the uglier it gets. The Ubuntu Server installer just made it so much cleaner.
gm10 wrote:My guess would be the package base might also be slightly different though. For example, my LM19 doesn't have mdadm pre-installed, which I would assume is what Ubuntu server uses to set up and run the array.
Ah, yes. I forgot about the need to check if mdadm was installed. Anyway, thanks for the feedback. I'm going off to checkout LVM RAID before decide if I need to put this idea into practice.
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