RAID setup at install ?

[vincen]

Hi

I plan to reinstall my desktop in Kubuntu but I'd like to do a RAID config for drives (2 SSD in mirror both for speed and basic reliability) but I don't see any option in install program to do that ! Is it possible ? even through terminal is ok but I didn't find any documentation about that !

Thanks

Vincèn

[oshunluvr]

AFAIK, Ubiquity (the installer) doesn't support creating RAID at installation. You have to do it in advance.

You don't say what RAID utility you're using. If it's a motherboard built-in RAID, the BIOS should be able to do it. If you're going to use mdadm, it will create a new device node (usually /dev/md0) and you just point the installer at that as the install device. I'm not 100% sure, but last I used mdadm (about 2008) you needed a separate boot partition.

I've used many different types of RAID over the years, so I have some comments. Feel free to ignore them;

RAID1 (Mirror) will not add speed and will actually slow down writes.
RAID0 (Striping) will nearly double your speed but doubles the chance of a data loss due to drive failure.
You don't get both speed with redundancy unless you use RAID 10 and even then, it's not as fast as RAID0 and it requires 4 devices.
Motherboard based RAID is a terrible idea IMO and I don't recommend it. Mostly because if your Mobo dies, so does your RAID access.

A couple points to consider; SSDs are already pretty fast. Unless yours are significantly slow, low-end drives I doubt you'll notice much in the way of real-world performance change by using RAID. The bottleneck is usually elsewhere. I am saying this as an SSD early adopter (back when they were tiny and expensive) and a long-time user of RAID at numerous levels. The risk and complexity of a RAID installation doesn't justify the end gain - again just my opinion, albeit an experienced one.

Finally, I have a suggestion. You can have it all with a simple file system change. I've been using BTRFS since it was brand spankin' new (before it was in the kernel). If you use BTRFS here's what you get;
You can:

Create RAID and change RAID levels.
Create a JBOD array (just a bunch of disks - no RAID just combined space like LVM).
You can add or remove devices (drives or partitions) from a RAID or JBOD.
Move your entire operating system and home from one device to another.
BTRFS uses subvolumes to segregate data and they can be snapshot-ed or used as backups natively (without external or additional software).

ALL of the above can be done on-the-fly, meaning without un-mounting or rebooting.

Plus, since BTRFS is supported by the kernel - no additional software needed and if your PC dies, any Linux distro can read and recover your files.

IMO, you should really consider using BTRFS. It much more powerful and user friendly than any kind of RAID or LVM. If you plan on using BTRFS in a RAID configuration, you will still need a boot partition (or a stand-alone GRUB partition, which is what I do) and you will need a swap partition.

Good luck with whatever you choose and welcome to Linux and KFN.

[oshunluvr]

BTW, 14.04 is nearing End-Of-Life and I don't recommend installing it. It's over four years old now. Why not use 18.04? It's much faster and more stable than 14.04 ever was IMO.

[vincen]

AFAIK, Ubiquity (the installer) doesn't support creating RAID at installation. You have to do it in advance.

Yep I know so my question

You don't say what RAID utility you're using. If it's a motherboard built-in RAID, the BIOS should be able to do it. If you're going to use mdadm, it will create a new device node (usually /dev/md0) and you just point the installer at that as the install device. I'm not 100% sure, but last I used mdadm (about 2008) you needed a separate boot partition.

So yeah it'll be RAID 1 for mirror and basic redundancy (have some separate backup system) and software based (linux, nothing from motherboard or any RAID card)

Finally, I have a suggestion. You can have it all with a simple file system change. I've been using BTRFS since it was brand spankin' new (before it was in the kernel). If you use BTRFS here's what you get;
You can:

Create RAID and change RAID levels.
Create a JBOD array (just a bunch of disks - no RAID just combined space like LVM).
You can add or remove devices (drives or partitions) from a RAID or JBOD.
Move your entire operating system and home from one device to another.
BTRFS uses subvolumes to segregate data and they can be snapshot-ed or used as backups natively (without external or additional software).

ALL of the above can be done on-the-fly, meaning without un-mounting or rebooting.

Plus, since BTRFS is supported by the kernel - no additional software needed and if your PC dies, any Linux distro can read and recover your files.

IMO, you should really consider using BTRFS. It much more powerful and user friendly than any kind of RAID or LVM. If you plan on using BTRFS in a RAID configuration, you will still need a boot partition (or a stand-alone GRUB partition, which is what I do) and you will need a swap partition.

Thanks a lot for explanations about BTRFS and I'll definitevely check it more in details. It makes me think about what I do with ZFS arrays Sad Linux can't be installed in ZFS native easily

[oshunluvr]

ZFS will never be in the kernel, so you're on your own with that one. BTRFS is much easier to use and maintain then ZFS could ever hope to be - IMO.

We have (had) a very active and talented member here who did some detailed work with ZFS and compared it to BTRFS:

https://www.kubuntuforums.net/showth...aying-with-ZFS

https://www.kubuntuforums.net/showth...g-other-things

The first link was his experiment, the second just some videos he found enlightening. I'm sure you know this, but any advice on the web more than six months old is suspect with regards to BTRFS (and most other things Linux) as the tools are still being developed and enhanced. In it's current state it's already amazing and continues to improve. I find the Arch Wiki to be the most up to date and informative.

I started experimenting with BTRFS when the tools version was 0.19. Once they committed to a format structure, I converted my server to it and I have continued to expand it's use everywhere I can. There's a BTRFS subsection on here that has lot's of threads. Enjoy!

[vincen]

ZFS will never be in the kernel, so you're on your own with that one. BTRFS is much easier to use and maintain then ZFS could ever hope to be - IMO.

To be honest all my ZFS arrays work like a charm and needs zero maintenance It was the goal with using ZFS anl also reliability considering large volume stored on that server (around 100To..).

We have (had) a very active and talented member here who did some detailed work with ZFS and compared it to BTRFS:
https://www.kubuntuforums.net/showth...aying-with-ZFS
https://www.kubuntuforums.net/showth...g-other-things
The first link was his experiment, the second just some videos he found enlightening. I'm sure you know this, but any advice on the web more than six months old is suspect with regards to BTRFS (and most other things Linux) as the tools are still being developed and enhanced. In it's current state it's already amazing and continues to improve. I find the Arch Wiki to be the most up to date and informative.

Thanks for video but don't be ashamed, it's some useless tests and put in evidence important lack of knowledges on systems tested !! Among them, ZFS in not an option on system without CEC ram excepted if you want to destroy all your datas quickly and efficiently !! or reading such statement: The RAID5 write hole probably isn't something Btrfs (or ZFS) can fix because overcoming that requires battery powered raid on disk controllers. denotes a total lack of understanding how ZFS works !

I started experimenting with BTRFS when the tools version was 0.19. Once they committed to a format structure, I converted my server to it and I have continued to expand it's use everywhere I can. There's a BTRFS subsection on here that has lot's of threads. Enjoy!

Thanks for pointing the section dedicated at BTRFS, I'll check it more in details to check how it can fit well on my reinstall of OS

For now I gave up on reinstalling that server as the Motherboard or something in system is killing my head I putted in it a NVidia basic video card but unable to use it... I succeeded to install one time Kubuntu using the IPMI video output but at reboot it never made it ! Purple screen stuck just after grub https://www.kubuntuforums.net/showth...d-graphic-card