RAID anybody?

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RAID anybody?

Postby HyperUniverse » 2019-09-03 14:42

Hi,

Anybody knows about RAID?

Would it be better to have a RAID1, or two independent drives that I will manually copy data from one to another?

Thanks.
HyperUniverse
 
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Re: RAID anybody?

Postby CwF » 2019-09-03 15:08

I had raid always in the early days, on DOS!, then NT, built it up to 80 pin backplanes with 13 drives...
Things change. There is no reason for raid on modern hardware. KISS
Do the spare drive thing, they're cheap. I still fill the ports with devices, but....
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Re: RAID anybody?

Postby debbieanne » 2019-09-03 15:16

If you have a lot of data that changes daily or more often, a RAID mirror is a good idea and costs no more in storage space than a dd or rsync daily backup. There are several tutorials out there that do a decent job of describing how to install mdadm and setup a new RAID mirror on an existing install where your OS/swap/uefi partitions live on one device (such as a fast SSD) and your data lives on your new RAID setup. If your data doesn't change often and you don't mind manual backups, a USB backup device is a good alternative. This RAID option protects your data, but doesn't protect your system from a failure of the SSD. That works for a lot of people.

It should be possible to have two or more RAID arrays on two identical hard disks that cover the swap and the root/home partition(s). With this sort of setup, it should be possible to lose one disk at any time and have the system carry on, protecting your boot environment, your swap space, your OS install and all your user data on /home. I am currently working on such a setup on a computer that until recently was running Windows 7 with that very arrangement and is now running MX Linux (AntiX OS based on debian). I am at this moment working out the detailed differences between my setup and one described by Falko Timme at https://www.howtoforge.com/how-to-set-u ... an-squeeze which is recent enough that I think it might work as written for debian and antix.

Why not just setup RAID mirrors from a LiveUSB and install MX Linux on those? I would ask the AntiX developers that question. Well, I already installed MX on /dev/sda and I would need to figure out how to make the installer recognize /dev/md0 as a device that it can partition and install the OS on. After researching a chroot environment approach that I thought was more difficult, I decided to follow Timme's approach, but unfortunately I am not yet finished. (How long does it take to dd a 1TB disk? Nine hours.) I'll keep an eye out here if there is interest to discuss Timme's approach and my experience with it.
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Re: RAID anybody?

Postby HyperUniverse » 2019-09-04 07:52

Thanks for replies,

I am more inclined to do a manual backup rather than RAID.
It's for long term storage, data won't change much at all.

I was thinking that RAID would be faster and less input from me needed.
But I am afraid of failures

In case of a hard drive failure:
How long to rebuild a 3TB hard drive?
And I'm thinking the same 3TB hard drive just to copy over (as backup), would take much less time.
So in case of a drive failure wouldn't I be better with a manual copy rather than have the RAID rebuild it?

What about in case of a motherboard failure?
Would I be able to just move all my RAID drives to a new motherboard and work straight away?
What if the same kind of motherboard is not available anymore? Will it work with a totally different one?
I know for sure that non-RAID drives would happily work on a different motherboard with no problems whatsoever.

And the last point that pushes me to the manual backup:
On a RAID you need to have all the drives connected at all times; that increases the chances of them to fail earlier.
Where on a manual backup I can disconnect the drives that I don't need, and only have one (or two) drives live, with all the backup drives packed nicely in antistatic bags in a leaded cupboard.

What do you think?
Thanks.
HyperUniverse
 
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Re: RAID anybody?

Postby CwF » 2019-09-04 15:04

I think you are on the right track.

The one thing to avoid is dependency, which you mention in a few ways. Overly elaborate solutions often discount this. Your mentions of rebuild time, leaving backup offline until needed, the ability to transparently swap any hardware, etc, are all on target.

My advice is to segregate as much as possible. With multiple ssd's on multiple ports this buys much of the speed advantage of raid setups with zero config dependencies.

Extra gooblygook you didn't ask for;
The idea is touched on in a few other recent threads, and I've teased elsewhere on the idea that File=Directory=Device, but I'm not sure many readers understood... I use qcow's for many data sets, that's a file. It is representative of a device, so can be written out to a device, a ssd. As either a device or a qcow2 file, it can be mounted as a directory.
So, the OS should be small and tidy with no user data. The backup method is then to image it to a file, complete. When configured so, the OS can boot on many machines. My images can boot and configure automagically to any motherboard I've tried. With user data elsewhere, these images are pretty static so a backup to image file happens a few times per year, after changes.
Next is the user data. You could simply pattern this after the standard user directories, /Documents, /Pictures, Videos, etc, or add a few mount directories to user(s) in that OS image. Then mount a device, or a qcow file as a device, into these directories. Then each category of data is backed up on it's own schedule, some change often, some rarely. The advantage of backing up a device (ssd) to a qcow2 file is compression. A disk device of any size yields a file no bigger than the actual data, sometimes smaller.
Yes, this method is primarily useful for a full virtual machine based system like I use, but the option to backup to image file is a universal solution. If you add an SSD to the system as /home for example, you could image that to a single file on your backup spinner hard disk, that's usually off. Then one day you upgrade that disk, simply image the file to the new disk, expand the partition to use the full space, and remount. Something like /Videos might be better just to directly copy since we all have terabytes of crap... On my backup spinner I have a few dozen qcow2's, many a few versions just in case. With that backup disk, a bootable usb, and a stack of new hardware I can rebuild a complex system fairly easy.
Food for thought!
Leave raid arrays to systems with 24/7/365 many user requirements with the requisite shelf of spare backup hardware. That unused shelf is where I get my hardware!
That reminds me, I buy a quality smallish SSD every so often and migrate the OS to this new disk. The old disk, hammered as an OS disk for the last year or more I then use as a data disk, living out its life 'less hammered'. I'm sad <120GB are hard to come by now.
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Re: RAID anybody?

Postby debbieanne » 2019-09-07 14:44

debbieanne wrote: I am at this moment working out the detailed differences between my setup and one described by Falko Timme at https://www.howtoforge.com/how-to-set-u ... an-squeeze which is recent enough that I think it might work as written for debian and antix.


Timme's article failed to help. Like all the other approaches I tried, there were omissions or wrong labels on modules (eg, mdraid when the proper name is mdraid1x). I found Raider (http://raider.sourceforge.net/) and it worked on MX Linux (based on AntiX based on Debian).

I couldn't get it to work with my original complicated partition plan, but when I reinstalled MX Linux using their defaults, Raider worked perfectly. It threw seven "missing module" errors but they didn't break anything.

Download the scripts tarball, expand it in /opt or wherever, run the install script and then run "raider -t -R1" and it will check and see if it thinks it can work. Then, if you agree, run "raider --run", shutdown when it tells you, swap your hard disk SATA cables, reboot and run "raider --run" again. Wait a long time for the script to sync the arrays and then Bob's your uncle (at least he was my uncle). There is even an uninstaller. AFAIK, it is under active development including plans to handle encrypted partitions and avoid the cable swap.
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