Question about RAID, and other things

RainOfPain125 · Sep 3, 2017

I've looked a little bit into RAID and all of that, but some things are a little unclear to me

In a RAID 1 both drives contain the same exact data. So does that mean the theoretical speed should be 2x since if the computer calls for half the data from each storage device?

Also, does RAID 1 automatically come with some sort of repair system? Ex if something in HDD 1 is missing, it will be replaced by the correct or non-corrupted file from HHD 2?

And if all the above is a "yes" why don't I hear about RAID a lot more? It sounds extremely useful with no disadvantages (well, besides the bottleneck if one HDD is slower)

rgd1101 · Sep 3, 2017

1)no. on reading might.
2)no
3)it complicate for most people.

https://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_1

USAFRet · Sep 3, 2017

RainOfPain125 :

In the consumer space, RAID is rarely the answer.

RAID 1 is a mirror. 2 drives with the exact same data. It only helps in a situation where you need 24/7 continued operation.
It does NOT do anything for the other fail modes.
Accidental deletion, malware, ransomware, file corruption. That just happens on 2 physical drives at the same time.

The OS and the user sees the RAID 1 as a single drive. Delete a file? Poof, gone.

A real backup situation gives you the opportunity to get that file back.

USAFRet · Sep 3, 2017

RainOfPain125 :

In this, no.
It reads and writes the SAME data from both drives. Not half and half.
Writing is often slower.

RainOfPain125 · Sep 3, 2017

USAFRet :

Writing might be slower, but I meant read speeds. It would only make sense that two HDD's could send different bits of information about the same file at the same time, to achieve as I said 2x the input, right...?

RainOfPain125 · Sep 3, 2017

USAFRet :

That's odd to me that the software wouldn't do that - repairing the other HDD's corrupted files I mean

It would make sense if malware or ransomware or deletion happened, but if a physical part of the hard drive was scartched or damaged (leading to non-working sectors / corrupted data) I don't see why HDD 2 wouldn't copy the already-existing files that are missing to HDD 1. It only seems more beneficial / useful / productive

RainOfPain125 · Sep 3, 2017

So say half of the data in a RAID 1 setup on a single HDD went corrupted. Your saying (if there was free space) the other HDD wouldn't try to replace the missing files...?

USAFRet · Sep 3, 2017

RainOfPain125 :

RAID 1 is a mirror. ALL the data exists on both drives.
If one drive were to die, the full complement of data still exists on the other drive.

The OS (and the user) only sees one drive (or file). There is no uncorrupted file to be restored from.
A RAID 1 is strictly for physical drive fail. It does nothing for file level fixes or restoration.
2TB + 2TB + RAID 1 presents as a 2TB drive to the OS. A single 'drive'.

Other RAID levels have more fault tolerance. And more complexity.

RainOfPain125 · Sep 4, 2017

USAFRet :

Which RAID level (if any) is like the one I'm describing? That uses 2 HDD's, and has file level fixes / restoration, and maybe read speed increases?

USAFRet · Sep 4, 2017

RainOfPain125 :

None.
That's not what they do. And anything beyond RAID 1 requires more than 2 drives.

By more fault tolerant, I didn't mean file repair.
Again, it is just for protection against the physical loss of a drive.

My NAS box is 4 drives, RAID 5. Data striped, with parity. All the data will survive the loss of 1 drive, with all data still intact. And it is, in theory, a bit faster than a single drive.

Read up on the various RAID levels here:
https://en.wikipedia.org/wiki/Standard_RAID_levels
https://www.prepressure.com/library/technology/raid

RainOfPain125 · Sep 10, 2017

USAFRet :

So there's nothing out there that does something like a RAID 1 where both drives have the same data, but can repair each other if file corruption were to take place, Ok.

And from what you say RAID is only for larger-deal things, whereas corruption isn't the problem, HDD's failing and no longer operating is the problem that RAID tries to fix (besides RAID 0 of course)

Makes sense now. It just bothers me nobody has made such a thing that I have described. A little off topic, but why do you think nobody has made such a software or whatever that I am describing?

Something like RAID 1 whereas the entire drive is used, and is mirrored onto the other(s) but a software of sorts notices on each individual drives if something is corrupted, ie if it calls file A from both drives (like RAID 1 in my mind would do since it see's it as one single drive) and file A on HDD 1 is missing or corrupted file A on HDD 2 should try to replace the file where it physically was on drive 1 (I assume just because a file off of HHD 1 is missing doesn't mean it will also vanish from HDD 2) and if it can't replace the missing data (assuming it's a bad sector) it marks that sector (as bad of course) and places the data on a non-used portion of the disc. I don't see any foreseeable bottlenecks or etc with the idea and am surprised nobody has done this. In theory (at least in my mind) it should achieve a 2x read speed, while also having the ability to automatically mark bad sectors, and replace corrupted data - which, imo, would be amazing for normal consumers that build / game / use computers, besides maybe a slower write speed

(well and of course a little drive and CPU usage used to mark / repair files)

USAFRet · Sep 10, 2017

Auto fixing of a corrupted file.
How does software determine what is "corruption"?

A volume encrypted with VeraCrypt is just random 1's and 0's. And looks exactly like a file or volume encrypted via ransomware.

Bad sectors? Sure...that is what RAID 1 does. Remaps every now and then.

Missing file? I meant to do that!

Data is not stored on a drive in "files". It is in blocks. Little tiny fragments, that when put together, constitute the "file".
These blocks can be all over the drive. This is what the file allocation table keeps track of, and what the weekly defrag tries to minimize.

RainOfPain125 · Sep 10, 2017

USAFRet :

Can you link something that proves / talks about RAID 1 remapping files n bad sectors n shtuff?

USAFRet · Sep 10, 2017

RainOfPain125 :

Actually, I was incorrect. RAID 1 doesn't even do that.
Physical drive fail. That's it. It has no way to know which bunch of 1's and 0's is the "correct" one.

RainOfPain125 · Sep 24, 2017

USAFRet :

RainOfPain125 :

Actually, I was incorrect. RAID 1 doesn't even do that.
Physical drive fail. That's it. It has no way to know which bunch of 1's and 0's is the "correct" one.

My very last question would be would you recommend I do a RAID10 setup if I wish to have both faster read speeds AND drive failover / redundancy or whatever you call it? I wish to set up quite a few servers, and that's why I am so interested on the topic of RAID.

USAFRet · Sep 24, 2017

RainOfPain125 :

Possibly.
As with all things, you have to tailor the configuration to the expected use and budget.
RAID 10 = 2 x RAID 0 arrays, mirrored. RAID 1 + RAID 0.

In one use case, a RAID 10 may be just the ticket.
In another, worse than useless.

For instance...my 4 bay NAS box is currently running a RAID 5.
I could reconfigure it as a RAID 10, at the expense of some drive space. Don't want to do that, so I don't.

And as always...a viable, automated, tested, backup plan is needed.
RAID of any type only protects against a physical drive fail.

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Question about RAID, and other things

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