RAID or not?

[sorcerer]

I only do residential work so, silly as it may sound, I've never actually seen a RAID array in the wild, so my question is - how do I recognise it if I should come across one?

I know there will be more than one hard drive but just because a machine has two drives doesn't necessarily mean that they are a RAID array, so does a RAID array physically connect to the motherboard differently somehow?

If I look in "Computer" on a residential machine I would normally see 'C:' as the system drive (and maybe other partitions too) and then an optical drive, so what would be different if the machine was RAIDed?

I'm asking because in a week or two a customer is going to bring his machine in for some work but when he phoned me the other day, he said that there are two drives in it but he doesn't know if it's RAID or not - so how will I know?

 

[mikeroq]

RAID varies between onboard controllers to add in cards.

Desktop wise it's going to most likely be built into the motherboard. Visually it will look the same.

However when the computer boots a RAID bios should pop up listing drives that are connected to it.

When in Windows a RAID volume will look just like a normal drive. However in device manager you may see a raid controller listed. For instance on my bench machine I'm using the Intel Raid. I see a "Intel Raid 5 Volume" under disks.

Best way to tell is in the RAID bios or the RAID software if installed. That way you will know for sure what drives are in RAID and the arrays.

Windows has software RAID but that will show as a Dynamic disk in Disk Management.

So if you don't see a RAID bios load, most likely there isn't RAID.

 

[mikeroq]

Example of Intel's software raid you will see on boot:

 

[G8racingfool]

The most obvious way to tell, is if the system has two disks and you only see one in the Computer Management (Windows). Explorer (aka: My Computer) will also only show the one drive. If you see two separate disks in Comp Management (ie: disk 0 and disk 1), the system is not in an array.

That said, there's two primary different ways to implement RAID: Hardware and Software. And a software RAID may show two individual disks in Comp Management. You'll need to check for any installed and running RAID software (Intel RST has a RAID component for example) to be completely sure it is not running in RAID.

As for looking inside the computer. If the RAID is run through the motherboard (as most residential desktop RAID setups are) you won't be able to tell by looking at the case as the drives plug in exactly the same way.

I'll go ahead and take a guess though that the disks aren't in an array. About the only residential people who would have a RAID array in their system would be someone with a gaming rig or an enthusiast who would definitely know they have an array setup. It's more likely to be a "C Drive + D Drive" situation.

 

[Alexey]

he most obvious way to tell, is if the system has two disks and you only see one in the Computer Management (Windows). Explorer (aka: My Computer) will also only show the one drive. If you see two separate disks in Comp Management (ie: disk 0 and disk 1), the system is not in an array.

Unless you encounter that funny feature where top halves of two disks are striped in RAID0 and bottom two halves are mirrored in RAID1. RAID controller will then export two LUNs, and you will see two disks.

You need to check disk names under Computer Management. Directly connected disks show up as their model names, RAID LUNs will show up as something else.

Also you need to examine BIOSes for settings and output.

 

[sorcerer]

That's great, thanks very much guys.

One last thing - before I start any job I always make an image of the drive in case I make a catastrophic mistake, so that I can always go back to 'square 1'. Is it possible to make an image of a RAID array and if so, how? In case it matters, I use Macrium Reflect for doing that.

 

[G8racingfool]

That's great, thanks very much guys.

One last thing - before I start any job I always make an image of the drive in case I make a catastrophic mistake, so that I can always go back to 'square 1'. Is it possible to make an image of a RAID array and if so, how? In case it matters, I use Macrium Reflect for doing that.

It depends on the RAID type. If it is a hardware RAID you'll need to make sure it is supported/seen by your backup tool. If it's not you'll need to add in drivers to allow it to be seen. Once it's seen/accessible however it's just like backing up a regular hard drive.

If it's a software RAID, image backups are a real pain because the RAID exists only on the software level. You'll need to make a full block-by-block image of each drive in the array and it needs to be done completely offline (ie: DON'T let the computer restart before you've finished backing up). With a software RAID, you also need to make sure the image makes it back onto the same drive it came from or you may risk corrupting the data.

 

[timeshifter]

It's more likely to be a "C Drive + D Drive" situation.

And C will be almost full with absolutely nothing on D.

 

[HCHTech]

Unless you encounter that funny feature where top halves of two disks are striped in RAID0 and bottom two halves are mirrored in RAID1.

@Alexey , Based on your post history, I have no doubt you are correct, but I have absolutely no idea what you are talking about here.

 

[Alexey]

Helps some?

Also if you want longer read than a block diagram

shorter one (only read the first page, the rest is benchmarking) - https://techreport.com/review/8059/intel-matrix-raid-explored

longer one from Intel - https://www.intel.com/assets/pdf/appnote/310855.pdf

It is called Intel Matrix RAID.

 

[HCHTech]

It is called Intel Matrix RAID.

This sound like.....a horrible idea. Not to mention the stuff of nightmares for data recovery folks. Some engineer's bright idea that should have been quashed by their boss before being made into an actual thing. I read both papers and I think this fails the complexity vs. benefit ratio test. Source: It's been out there since 2005 and I've never heard of it, much less encountered it in the wild. Interesting only on an intellectual level, says I.

 

[DataMedics]

This sound like.....a horrible idea. Not to mention the stuff of nightmares for data recovery folks. Some engineer's bright idea that should have been quashed by their boss before being made into an actual thing. I read both papers and I think this fails the complexity vs. benefit ratio test. Source: It's been out there since 2005 and I've never heard of it, much less encountered it in the wild. Interesting only on an intellectual level, says I.

Nearly all NAS's use something like this. A small RAID 1 at the beginning of all the disks so the NAS can still boot as long as any drive is good. Then another RAID level (RAID 0, 5, or whatever you set) of LVMs for the rest of the disks capacity for all the user data.

Not that big of a deal for data recovery if you know what you're looking at.

 

[Alexey]

This sound like.....a horrible idea. Not to mention the stuff of nightmares for data recovery folks.

With two drives in desktop, this is useless. With four drives, maybe not (can I has a hybrid of RAID10 and RAID5?). With more drives and in more specialized storage units (NASes), this is widely used. Data recovery folks, well, we just deal with it. It is not even the worst of the nightmares.

 

[Markverhyden]

Given that the OP says they're dealing with consumers this is my take.

99.9% of consumers that have RAID actually running are using software RAID. So the onboard controller is similar to what @mikeroq posted.

For backups and data recovery this is more difficult. Booting from just a regular *nix, like Clonezilla, doesn't see the array. It'll just see two discs. If it's a mirror then no problem. But if it's stripped then it'll require imaging each disc and then rebuilding, hopefully, the array. Fortunately some data recovery apps, like R-Studio, will recognize an array from images.

Having RAID in a consumer machine is very rare. I long ago lost count of how many machines I've worked on over the years. Easily 10k. Out of those I've only seen maybe a dozen that had RAID. Most of them were Dell's, back when they were pushing them on consumers with the Intel chipset on the motherboard. Funny thing is most of them were not even setup out of the factory or had broken and the EU didn't even know they had a RAID.

 

[HCHTech]

Nearly all NAS's use something like this.

I didn't know this (another entry in the massive file of things I don't know*) - I guess it makes sense in that context....Frankly, it never occurred to me to wonder where the NAS OS actually was on the (mostly) Synologys we setup. I've dealt with Buffalos and a few QNAPs as well. I guess I always thought the OS was on some non-volatile memory or something - you buy the things without disks after all and don't have to do an install of the OS first, you just mount the disks and turn them on and it loads the OS.

*"I call this my "Thomas Edison File" - there is a quote out there that I hope is his: "We don't know one-millionth of one percent about anything." QED, man, QED.

 

[GreyWolf]

@HCHTech I saw worst in the evil department of Raid ideas https://www.reddit.com/r/DataHoarder/comments/7w12p7/someone_finally_did_it_sd_card_raid_0_array/

 

[mikeroq]

If it has the Intel RST which is a "fake RAID", linux should support it with mdadm. mdadm since Kernel 2.6.27 and 3.0 of mdadm supports DDF and Intel Matrix RAID (now Intel RST)
If it's a software RAID like dynamic disks in Windows then linux is just going to see the individual disks.

Software RAID can be many different things:

• mdadm
• Windows Dynamic disks
• Part of the file system like ZFS

Then you have "hybrid RAID" or "fake RAID" like the Intel RST. Combines some hardware and software. Firmware handles booting and once the OS loads the Intel drivers take control of the RAID.

Then you have "hardware RAID" which will involve a dedicated controller card but at the lowest end is barely better than onboard RAID.

 

[Alexey]

I saw worst in the evil department of Raid ideas

 

[GreyWolf]

@Alexey I had seen that one what's worst that setup works but on low duplication more than x usb's and it becomes pointless the other one I posted was reviewed by linus and well it's so flimsy that data corruption is practically guaranteed heck the clips seem worst than trying to fix a apple watch screen.

But ya if people are crazy enough to install such a raid setup you deserve horrible data loss.

 

[labtech]

One other quick trick would be math related with regard to size of the volumes.
Say we have one main logical volume (most home users do so), we can calculate the size of the volume as follows:
-For RAID 0 & JBOD configuration, the capacity of the volume will be = ~capacity of one drive x2
-For RAID 1 configuration, the capacity of the volume will be = ~capacity of one drive

So, asking the customer a couple of simple questions may help. For example:
- What was the storage capacity of the volume/partition? If it is higher than the capacity of one drive, then you are likely dealing with a RAID0 or JBOD config.
- How much data was on the volume saved? Or how full was the volume? Again, if more than the capacity of one drive, again, we will likely be dealing with a RAID0 or JBOD.

Another suggestion: If you plug in one drive at the time and they show correct volume size, shows data and the data is good, then it is likely a RAID1 config (RAID 1 is mirror, so identical, or near identical if they have mirrored properly).

Lastly, if this is a machine that was bought with a RAID config, you can look up the model and the RAID info may be explained in the details.

If these don't do the trick, then more advanced troubleshooting is needed, typically involving more advanced tools and expertise. Perhaps partnering up with a data recovery specialist in your area may be beneficial.