Thanks, bro! I've already started copying data onto the RAID array, so I don't think the lack of partitions is a big enough issue to warrant rebuilding. I intend to document my steps anyway to preserve my future sanity. :-)
Good to know I was on the right track in using mdadm rather than LVM, and I'll keep it in mind that I can use LVM over MD in the future. In this case we only wanted one big (redundant) filesystem anyway.
I'm actually setting this up remotely through a VPN on a system in Miami, so I preferred to stick with CLI tools as much as possible. I had thought of setting up a single partition on each disk using parted, as some tips online suggested that, but I figured why bother if the DigitalOcean tutorial didn't mention the need to do that. I probably will add in that step the next time I set up a similar array. I hadn't heard of gdisk before, so I'll check that out.
On 10/04/2018 09:42 AM, Gilbert E. Detillieux wrote:
I think the tutorial is complete enough. The only thing I'd do differently is create appropriate partition tables on the raw disks (GPT if the disks are >2TB or if you need to use GPT for other reasons, but the older MS-DOS partition tables would be fine otherwise), set up one partition on each drive and tag them with the applicable partition type to indicate they're MD RAID partitions, and use the device names for the partitions rather than the raw drives in the mdadm commands. While this isn't necessary, I think it would help in post-mortem recovery, and in keeping your sanity when you're (or someone else is) trying to figure out what you did a few years later.
LVM has some nice features to offer, e.g. if you anticipate wanting to add more capacity to this file system in the future, or you want to split a large array into multiple file systems. But for simple use cases, I wouldn't bother. If you do use LVM, don't use its RAID features; use LVM over top of MD.
If you go with GPT partition format, and don't want to deal with the arcane syntax of parted commands, there are alternatives: gparted for the full-GUI, Partition-Magic-like experience, or gdisk for a simple fdisk-like, retro, text-menu-based interface.
Gilbert
On 04/10/2018 8:33 AM, Gilles Detillieux wrote:
Circumstances finally forced me to bite the bullet and learn something I had been putting off for too long: setting up a RAID array under Linux. I'm almost embarrassed, now that I've done it, that I waited so long because it was way simpler than I'd imagined. I thought I'd have to figure out all kinds of magic with LVM, parted, and mdadm, but I found this tutorial that showed a simple set of mdadm commands to set up RAID 1:
https://www.digitalocean.com/community/tutorials/how-to-create-raid-arrays-w...
This was actually one of the simplest scenarios: the system had an SSD for the root/boot partition, and two 2 TB hard drives for data storage (/dev/sdb & sdc), so I just needed to set up RAID 1 and not worry about the intricacies of booting from RAID. So, software RAID seemed like the quick & easy way to go with a minimum of fuss.
Now the nagging question: is it really this simple, or does the tutorial above oversimplify and omit some important steps? Can someone with ample RAID and mdadm experience advise or provide tips on anything else I should do or lookout for?
Thanks, Gilles