RAID 5, explained

[chazter6]

I have never understood types of RAIDuntil now. Thanks for a great explanation of RAID 5

[2008rames]

hi,

In case of 3 HD each 1 TB,output yield will be 2 TB and one for parity.

What happens in case of more than 3 HDs.

[sn0le]

@2008rames: As I've written in the description of the video. The total capacity of the array is: (n x cs) - cs = tc n = number of drives cs= capacity of the smallest drive tc = total capacity If you have 5 x 1.5TB it would look like this. (5 x 1.5) - 1.5 = 6.0TB If you have 4 x 1TB it would look like this. (4 x 1) - 1 = 3.0TB Etc etc...

[sn0le]

@InfernoDragon56: As far as I know, yes. But I'm not sure it's "worth" it. Huge cost, and the speed of the array will probably be limited by the RAID-controller. I may not be able to calculate the parity bits fast enough to give full use of the SSD' high performance. But I haven't tested it, so I'm only guessing and may be terribly wrong.

[InfernoDragon56]

@sn0le Does this operation still work with 4 ssd's?

[AinaRaoelina5]

What do you XOR data with if each disk in the array is not filled? Or do you XoR it at all in that case?

[airbrat]

Quick question. If you have 3 drives, each 500 GB, does that mean your operating system sees a total of 1.5 TB? Or does it only see 1 TB and uses the 3rd disk as redundancy?

[sn0le]

@airbrat:

With RAID 5 it will show 1TB. All disks are used for redundancy, but just 1 for each "set" of data.

[naughtysri100]

You simply awesome..i have been struggling for longtime to understand this "parity", just cleared my mind..thanks a lot..

[vicharenitin]

Superb sn0le ..have been searchin for such a explanation for years

impressed ..

thanks a lot

[phyx726]

Thanks for posting this. As soon as you said exclusive OR everything started making sense. From a coder's perspective, this its a lot easier to understand with a XOR table. I actually had an easier time thinking replacing the 1/0's with true/false. Thanks, great presentation.

[coachmark2]

This makes really good sense. I know what parity means now instead of some abstract explanation. Good job.

[Budahnb]

Fantastic example!

Thanks for the vid!!

[eddimull]

Thanks for ACTUALLY explaining what goes on instead of what is good and bad about it in theory

[pardeephappy]

good one, easily catchable

[sn0le]

@pardeephappy:

Thanks. :)

[w3b5h06un]

I think you really should make a RAID 6 video, as this is way better data protection and recovery than RAID 5 .. also the way to add a new drive into the array if a drive or 2x drives go down

[w3b5h06un]

by the way, you have the best explanation of RAID 5 to date. Well done :)

[w3b5h06un]

RAID 6 is exactly the same as RAID 5 but writes parity 2 parity bits on each drive so that if by chance you have 2x drives go down you would be data safe yes?

[mo7senses]

Hi,

I've a quick question - what if i've raid 5 have 10 disks and lets say 2 disks goes down? will raid 5 collapse?

Also, what would be the best way to upgrade RAID 5 storage disks (from 146Gb to 300GB SAS) without downtime and breaking RAID 5.

would appreciate if you could help.

TIA

[paulph12002]

Good explanation of Raid 5, Snole. Would I be correct in saying that write speeds are slower with Raid 5 than Raid 0 because of the need to write and modify parity data on each read/write sequence? For that reason, I use Raid 0, and minimised the risk of data loss by using 2 identical new WD Caviar Blue HDDs, with any important data backed up onto a HDD that's not part of the Raid.

[sn0le]

@paulph12002:

Thanks for the feedback.

Well, I haven't tested RAID 5 array (with minimum 3 HDD's) vs a RAID 0 array.

But from what I understand, a RAID 0 array will always be the fastest since no parity bits need to be generated/calculated.

Even with a non-RAID 0 array one should have backup. A RAID 1 or RAID 5 array doesn't eliminate the need for backup, since data can still be lost if files are corrupted or multiple drives fail.

So for max speed, RAID 0 is the way to go.

[justryingz]

thank u , u explained it very easy

[k1piee]

Wow this explanation was awesome! Before I had no idea how the hell I could lose one drive and still have the data left on my raid array but you explained it so well that I really understand now :D

[sn0le]

@k1piee:

Glad I could help. :)

[chernanq88]

Estoy asombrado la manera tan clara en que explicas el funcionamiento de RAID 5, mis felicitaciones.

Im amazed the way so clear you explain how RAID 5 works, congratulations!

[sn0le]

@chernanq88:

Thank you for your comment. :)

Glad to hear that my video was helpful to you.

Cheers!

[dirtydoug]

Hi very informative video but im still new to raid and trying to learn, hope you can answer my questions

1) so raid 5 is safer than raid 0 but raid 0 read/write faster than raid 5, is that correct?

2) raid 5 is only fast on read but slower on write?

3) I like to use 3x60gb ssd as raid but im confuse which 1 to use raid 0 or raid 5, i use this 3 ssd for my OS only and to make my applications load faster at startup but if raid 5 will slow down conversions that wont help.

i really need help TIA

[dirtydoug]

@dirtydoug i just want to add that the apps im using were adobe products, so conversion means video rendering, photo etc that involves multimedia :) if its going to seriously slow down with raid 5 i will just go with raid 0 but im too lazy to install again once it fails me. lol

[sn0le]

@dirtydoug:

I am not very familiar with the adobe products.

There are probably many ways to set up an editing system to achieve maximum performance.

So the best chance is to see what experienced adobe users do.

[sn0le]

@dirtydoug:

1. Yes

2. Yes (but still faster than a single drive).

3. If you need speed, use RAID0. RAID5 will be faster than a single HDD/SSD, but also give you redundancy.

[panktambe]

nice explanation.... Thanks for such a nice video...keep up the good work !!

[PossiblePoison]

Question, since raid 5 requires minimum of 3 drives..do I have to get all 3 at the same time? I mean, right now I can only buy one 2TB drive..and I'd like to use it in the meantime. When I buy the other two, will setting up a raid (5) system remove the all the data from drive #1?

Thanks

[sn0le]

@PossiblePoison:

You can use different drives bought at different times. No problem.

The optimal solution is that they are the same size and comparable in terms of performance (seektime, readspeed, writespeed etc).

[PossiblePoison]

@sn0le Thanks for the really quick reply :) Yeah I'm planning to purchase 4x2tb (all the same model) but like I mentioned a few days ago, I'm building my own NAS so with the case+cpu+ram i've only got money for 1 drive to begin with..but I'll keep buying them!

Anyway thanks for this video, and also thanks for replying! So many tutorials on here where the uploader never replies to the questions in the comments hehe

[sn0le]

@PossiblePoison:

No problem. I try my best to answer any questions and reply to comments when I have the time.

I guess your timing was very good tonight. :)

[PossiblePoison]

Thanks for the video! I've decided a DIY is better than buying a pre-built NAS :)

Freenas, freebsd etc..so much better!

[sn0le]

@PossiblePoison:

Sounds like a fun project.

There's a lot of good solutions out there for people that want's to make their own NAS.

One just have to have the time to do the research and time to get stuff working.

Good luck, hope it turns out well. :)

[ashwinwriter]

Excellent explanation. You didn't sound as smooth as other professional tutors do, but what you explained is by far well understood. I really appreciate it. Good job!

[sn0le]

@ashwinwriter:

Hehe. You are right. My biggest problem is the language.

In some of my first Youtube videos I tried to script what I was going to say.

But that sounded awful.

So I started just talking without a script, and sometimes I struggle finding the right words, and my grammar might be bad.

But as long as people understand what I am trying to say, I am a very happy man. :)

[2000jago]

This may be the best explanation of the exact concept of parity I've ever seen. Well done!

[sn0le]

@2000jago:

Thank you. Very nice to get feedback like that. :)

[gt0703]

Excellet job. I really appreicate guys like you taking the time to help many of us.

[sn0le]

@gt0703:

No problem. :)

[clariion11]

Thanks a lot....

I had spent hours to understand what raid 5 is and what exactly parity is...

I have referred a lot of documents online, but nothing helped.

Your video is just amazing.

In less than 10 minutes, you made the concept crystal clear.

Thanks buddy....

[sn0le]

@clariion11:

Glad that my video helped you out. :)

[swaroopt]

Thanks for a very good video on RAID5.

[sn0le]

@swaroopt:

Glad you liked it. :)

[Denkmuster]

Thank you for the explanation. It is the first time I really understand what parity means. Sorry for my bad english.

[sn0le]

@Denkmuster:

Keine problem. :)

[FrankfurtamMainxxl]

I want to setup a RAID...

I want to put 4 harddrives in a raid 0 , but the 4 are devided up into to groups of 2 in RAID 1 ... does that work?

[sn0le]

@FrankfurtamMainxxl:

You can use RAID 0+1 or RAID 1+0.

It is a combination of RAID 0 and RAID 1.

It requires 4 drives, and will give you very good read/write performance.

You'll also have redundancy in the RAID-array, so that if a drive fails your data is still safe.

[FrankfurtamMainxxl]

@sn0le thanks :)

I'll be setting up a raid 10 then.

I got 4x1TB drives here so I guess that will do it.

Do you know any good raid controller?

[2DeCipher]

Nice explanations. Key thing to note is that RAID can be provided in software or hardware - and the speed of read and write depends largely on how the controller is implemented.

[sn0le]

@2DeCipher:

Very true.

My knowledge is very limited (I feel) about the subject.

I made these videos to show how basics of the different RAID architectures.

I was looking into setting up my old PC as a fileserver, and tried to find out what RAID type I should use.

And I was frustrated that I couldn't find any simple explanations on the subject.

So I Googled alot and finally started to understand the basics.

But as you said, performance depends on many factors.

[sn0le]

@2DeCipher:

PS: In my RAID introduction video I mentioned that a RAID controller can be either hardware-based or software-based.

[MrImaginecreativity]

This video was the only thing i needed to understand Raid 5, thankyou for uploading it

[patrikk777]

Raid 5 vs Raid 0 in terms of speed?

[sn0le]

@patrikk777:

I haven't done tests with RAID5 my self.

I would only have to assume that a RAID0 will be faster since the RAID-controller doesn't have to calculate the parity bits.

I might be wrong about it though.

RAID 0 offers high R/W performance at a relatively low cost. But it has 0 redundancy.

RAID 5 offers good R/W performance at a slightly higher price because of the extra space needed for parity bits. But it does offer redundancy.

[patrikk777]

@sn0le OK, thank you very much. I'll have to do some digging. BTW, do you need 4 drives for RAID0+1? And does RAID0+1 have any benefits over RAID5?

[sn0le]

@patrikk777:

RAID 0+1 and RAID 1+0 requires minimum 4 drives.

The benefits are that they're faster than RAID 5. And the data MIGHT survive multiple drive failiures, as long as they are on the same side of the mirrored set. (At least for RAID 1+0).

The disadvantages that they are complex to set up and expensive since you must have 4 drives and only get 1/2 of total disc capacity.

But I am no expert in this, so you shuld really do some extensive research before you decide what to use.

[askloglog]

raid 0 for os and commonly used programs...

raid 5 for storage and other programs = awesome system!! :)

this is a really good way to break down how the raid system works good job

[RoyHess666]

Thanks for that explanation, I'm german and your english spoken in the video is very clear and understandable!

[sn0le]

@RoyHess666:

You're welcome, and thanks. :)

[gnabeel]

Raid 0 is the best :)

[sn0le]

@gnabeel:

RAID 0 is good for speed, and gives you the highest capacity of the various RAID types.

But it offers no redundancy, and should only be used with that in mind.

If you need a fast scratch-disk for video editing, RAID 0 is a good choice.

If you need data to be safer than on a single HDD, RAID 0 is not a good choice.

So it all boils down to the needs one has. RAID 0 isn't necessary the best. ;)

[gnabeel]

@sn0le, I'm good with backups. All I want is maximum performance :D

SSD is much better choice, but its too damn expensive. About $2,000 for my requirement. So I think I will try out RAID 0, Hope all goes well. Thanks for your help :)

[chockn]

@sn0le technicly speaking. raid 0 is not a real raid at all. why you ask?

well it lies in the name. redundant array of independent disks. is raid 0 redundant? no its not :)

[sn0le]

@chockn:

I did mention that in either the RAID0 video or in the video I made as a introductionary video to all my RAID videos.

RAID0 isn't redundant, but for some reason it is still counted as a RAID architecture.

[yannquix]

Awesome

[Yales111]

THX @ sn0le !

[Yales111]

THX sn0le !

[rmehra2]

Way of Explaining is very nice.

[MotionFur]

The video was very clear, thanks for uploading.

[sn0le]

@MotionFur:

You're welcome. :)

[metoyoou]

Very well explained. Thanks ;)

[sn0le]

@metoyoou:

My pleasure. :)

[80amnesia]

cool

[sn0le]

@80amnesia:

I know! :P

[Willanhanyard]

Now I get it! Thanks you so much! I didn't know about raid 5, now I'm going to be upgrading to it. Thanks!

[mdwasim]

Thanks alot for such a good and in depth explaination. :-)

[ADOLFORESTREPO]

finally I got the raid 5.

Thanks

[1TheMainMan1]

now i fully understand raid 5 thank you so much :)

[dakrisht]

Great video, great explanation, thanks for that. Raid 5 is coming in clear for me now

[Wingz136]

How does the RAID controller distinguish the first half of a byte, the second half, and the parity bits?

[sn0le]

@Wingz136:

I got that question a few weeks back.

And to be honest, I am not able to explain how.

I Googled and found some explanations on how a RAID controller will determine if data is paritybits or parts of the data.

However, the explanations were so complicated that I hardly understood them. :/

[shvetsov1987]

Great video! Thank you!

[thegreyvingian]

DAMN THIS WAS AWESOME.Now I understand Raid 5, Thanks!

[sn0le]

@thegreyvingian:

:-)

[skovacs]

ooops did not mean to post twice

[sn0le]

@skovacs:

Hehe. No problem. :)

[skovacs]

hey that was a great video. i just have one question say i make a raid 5 hdd with 3 500gig hdd`s at a later date can i add another 500gig hdd with out having to format all 4?

[skovacs]

hey that was a great video. i just have one question say i make a raid 5 hdd with 3 500gig hdd`s at a later date can i add another 500gig hdd with out having to format all 4?

[sn0le]

@skovacs:

As far as I know, expanding an existing RAID5 array is not possible.

You'd have to backup everything and configure the array from scratch.

This is a definite downside to RAID5, and Netgear has made something called X-RAID that allows for adding more drives and still keep redundancy.

Not sure how X-RAID works though....

[semih007]

Finaly i understand raid 5. :) Thank you.

And can i translate this video to turkish ? I will post to my blog i will give a link to this video.

[sn0le]

@semih007:

Glad my video was helpful.

I'd be happy to let you translate it to Turkish. :)

[sn0le]

@r1ccardo:

The drives can be various sizes and speeds.

But the array's capacity will be dictated by the smallest drive.

If you have a 500GB, a 1000GB and a 1500GB HDD, the total capacity will only be 1000GB.

So it would be a huge waste.

Using a SSD is possible, but a complete waste, since the performance of the array is limited to the slowest drive.

[desormais]

Great explanation! Can you do one with RAID 6?

[sn0le]

@desormais:

Thanks.

I might do a video about RAID 6 and/or other RAID types in the future.

Right now I'm just enjoying this nice summer. :)

[vjo219]

very well explained , Thanks a ton, but how does it work when there are more than 3 disks, in that case data 1/nth part to each disk, if there are n disks?

[sn0le]

@vjo219:

Thank you.

If there are more than 3 disks the RAID array will function at a higher rate.

The total capacity will follow the formula in the descriptionbox.

Lets say you have 6 harddrives, each of them 1TB.

The total capacity of the array will be 5TB, since you'll always lose the equivalent of 1 HDD because of the distributed parity.

[vjo219]

@sn0le- very well explained , Thanks a ton, but how does it work when there are more than 3 disks, in that case data 1/nth part to each disk, if there are n disks?

[tokugawashindaru]

Cool. Do you have any security certifications yet? I'm working on Cisco's security, but I also like learning things that are a bit more outside of the box. How is the economy up there? Is it very open to either programmers or networkers?

[tokugawashindaru]

@tokugawashindaru

maybe send me an email reply?

[TheFilm35]

such a good tutorial :) well done

[sn0le]

@TheFilm35:

Thank you. :)

[paxat]

Very helpful, I always wondered how the parity was calculated. I still wonder how it knows where the parity is though.

[sn0le]

@paxat:

Thanks. And a VERY good question. :)

I actually had to Google a bit, and I did find some good guides to how a RAID 5 finds out which data is the parity bit and so on, and thus recovers the data in case of a disk failiure.

However, the explanation is VERY complicated, and I would probably have to make an entire video to show how it works.

And I'm not even sure I fully understand it myself. Lol.

I think I'll just say that the RAID controller figures it out. Hehe. :)

[SutkasFan]

"Officially they are to be called SATA 3Gb/s and SATA 6Gb/s."

Thats true but lot of people use the terms "SATA 2 3G/s" and "SATA 3 6Gb/s"

I have seen that terms on lot of sites...

[sn0le]

@SutkasFan:

I know. Many webshops use the terms SATA2 and SATA3.

But it doesn't mean it is correct. :)

It's like my parents and most old people refer to the computer casing as "the harddisk". At least in Norway.

They seem to think that the harddisk is the entire computer. :)

[SutkasFan]

@sn0le

Haha, my mum use the term "the monitor" to describe the whole PC.

She thinks that all parts are in the monitor :)

[SutkasFan]

Can you make RAID between a SATA 2 HDD and SATA 3 HDD ?

[sn0le]

@SutkasFan:

Yes. But the array's performance will be limited to the slowest drive.

On a sidenote, there is no such thing as SATA2 and SATA3.

Officially they are to be called SATA 3Gb/s and SATA 6Gb/s.

This is according to The Serial ATA International Organization (the guys behind the SATA-standard).

[SutkasFan]

Is it faster than RAID 0 ?

[sn0le]

@SutkasFan:

The speed depends on how many drives you have. That also applies for RAID 0.

RAID 0 will be the fastest RAID-array, but it is non-redundant.

So if you lose one HDD, the data on the entire array is lost.

RAID 5 is almost as fast. It is slower since it has to generate the parity bits.

The advantage for RAID 5 is that if a HDD dies, your data still remains intact.

[SutkasFan]

@sn0le

I know that for RAID 5 you need at least 3 drives,but i don't know how many drives support RAID 0.

So which RAID would be faster on this drives in SATA 3 6Gb/s

two Crucial RealSSD C300 64GB and two WD Caviar Black 1TB,

those 4 drives in RAID 0 and RAID 5, which one would be faster ?

[tokugawashindaru]

Are you Scandinavian? also, what do you do in the computer industry?

[sn0le]

@tokugawashindaru:

I am Scandinavian, yes. Norwegian to be more precise. :)

And actually I don't really work in the computer industry.

They're just my hobby.

Allthough, I have been installing various end user systems on computers in various jobs like Security systems etc.

[killerstef22]

is it possibhle to use 2 harddrives with one volume being the double of the other?

[sn0le]

@killerstef22:

Not that I know of.

Besides, there would be no point.

If the drive with the 2x size fails, you will lose all your data anyway.

So you could just use striping instead.

Unfortunately, striping gives the best capacity when the 2 drives are the same size.

1x500GB + 1x1000GB will only give you a 1000GB RAID 0 array.

So not much point in that either.

[mttube321]

hi super explanation.. i checked all your raid videos, they are excellent. While you post in future, or update your videos, please include following info ... what if 6 ( identical or dissimilar disks capacities) and what if N no. of disks

[kidowner]

ok so basically raid 5 is basically raid 0+1 but with only 1 hdd for backup?

[sn0le]

@kidowner:

Well, I wouldn't put it that way.

A RAID 0+1 array with 4x1TB disks will give you 2TB of storage.

A RAID 5 array with 4x1TB disks will give you 3TB of storage.

So RAID 5 has less capacity yield.

But both RAID 0+1 and 1+0 can sustain more than 1 HDD failiure, as long as one of the mirrored sets are intact.

RAID 0+1 gives the best RW performance, and RAID 1+0 gives read performance that is at the level of RAID0.

[kidowner]

@sn0le yea but im not talking about capicity. Is there any raid that is basically a raid0+1 but with 3 hdds? i mean. coz i want the raid 0 capability and the backup of the striped information..

[sn0le]

@kidowner:

I am by all means no expert.

But as far as I understand it you would have to go for RAID5 if you want to get 3 drives working like that.

I was concidering RAID5, but I have too little experience with this, and as far as I could understand a RAID5 has to be tweaked in terms of stripesize.

If the stripesize is to small, you'll lose RW-performance.

If the stripesize is to big, you'll lose capacity.

And the correct size depends on the filesize of the files you will put on that array.

[kidowner]

@sn0le well ok. i dont care about size im gonna buy 640 GB ones from WD.. and 500GB for me is enough so..

[sn0le]

@kidowner:

If your RAID-controller supports RAID 0+1 or RAID 1+0 you'll have a very good redundancy and performance with 4 drives.

And you'll get a total of 1280GB (957 GiB).

[kidowner]

@sn0le well the problem is that my mobo wont support that much sata ports.. I mean i will already have 2 ssds in raid 0 for windows and major applications..

+ 2 Optical drive disks

+ 3 HDD

+ E-sata..

= 8 satas

[sn0le]

@kidowner:

You can get cheap PCI-express SATA-controllers with RAID functionality.

But the best solution is to get a good RAID-card.

They have onboard RAM to store info about the RAID-array etc.

Cost a bit of money though.

[kidowner]

@sn0le yea well i dont have lots of money so..

[sn0le]

@kidowner:

Hehe. Me neither. So I took the easy route and mirrored 2x1TB on my fileserver.

I could go for a 3x1TB RAID5, but RAID0 and RAID1 is alot easier to set up.

And I have an external 1TB drive for backup of the RAID.

Because a RAID doesn'r remove the need for backup.

A lightningstrike may fry your entire computer, with HDD's.

And then any RAID, even with spares, might not do you any good.

[kidowner]

@sn0le yea true.. so i might just go with raid 0.. i backup everything on cd's anyway.. so..

[sn0le]

@kidowner:

In more detail.

A RAID5 array creates parity bits of the data that it writes to the disks.

A RAID 0+1 will just split the data in half, to stripe them, and then simply mirror them

A RAID 1+0 will mirror the data on 2 HDDs and then stripe the data onto 2 other HDDs.

[produKtNZ]

A question/statement. In your example of Parity calculations(4:00), haven't you effectively written NO data? (with respect to 0's meaning off and 1's on in binary) ??

I might be confused here =\

[sn0le]

@produKtNZ: Data can be either 0 or 1. 0 means "off" and 1 means "on", sort of. It is the state a bit can have. It has either the value 0 or 1. As an example: The letter "a" in the ASCII-table is 01100001 in binary. The letter "b" in the ASCII-table is 01100010 in binary. And the list goes on. If you were to make a parity bit out of these 2 characters, it would be: 00000011. @4:00 the parity bits are data, even if they are "0000". And they are crucial for any rebuild of the original data.

[fakinade1]

would you recommend using a raid 5 system lets so for making a documentary film and want to protect all of your footage. that would be our only source of storage (or back-up) and thats it. or would you suggest an alternative system. Great video. really cleared things up. Also how well do you need to understand how to use it to use it. or does it do all of this automatically. for instance could we simple drag and drop data into the raid.

Thanks! keep up the good work!

[sn0le]

@fakinade1:

Once you have created a RAID-array it will be visible on your operating system as a normal disk. So you can drag and drop files/folders to it like on a normal disk.

Having a RAID doesn't mean you don't need backup. Even with RAID5 you could experience a failiure that will make it impossible to retrieve the data.

I found that RAID5 needs more optimalisation (stripesize etc) to get optimum performance, so I put 2 HDD's in RAID1 (mirror) and have 1HDD as external backup.

[sn0le]

@fakinade1:

Setting up a RAID5 array is not too hard (depends on the RAID-controller).

You specify which drives are a part of the array, and the controller does the rest.

You can specify that 1 or more HDDs are "spares".

So if one HDD dies, the array will automatically rebuild, using the spare HDD.

However, stripe size is crucial. It needs to be tweaked to a size that matches the files you have.

Using a stripesize to small or too big will cause performance loss or low capacity yield.

[sn0le]

@frwgt350net:

For software RAID, the choices are a bit limited. There are ways to make XP support more software RAID types.

If you have a RAID-controller, either as a PCI/PCI-express-card or built in to the motherboard you'll get all the types of RAID that your RAID-controller supports.

On my own fileserver I use the built-in Intel Matrix RAID-controller (on the motherboard) and the software that comes with it. No problem.

[guzano21]

Glad that there is people that shares their knowledge on technical areas like this. Thank you.

[sn0le]

@guzano21:

I am just happy that people has learned something from my videos.

Thats why I make them. Especially these RAID videos. :)

[maximefcom]

many thanks !!! very informative video !!!!

[sn0le]

@maximefcom:

Thanks for the feedback. Much appreciated! :)

[s4iko1337]

so raid 5 is same as raid 0 + raid 1 with 4 hdd's except raid 5 needs one hdd less and has lower acces time ?

[sn0le]

@s4iko1337:

RAID 5 with 3x1TB HDD's will give you 2TB of space.

RAID 0+1 recuires 4x1TB HDD's to give you 2TB of space.

So you're right about RAID 5 requiring 1HDD less.

When it comes to access-time I can't say for sure, since I have no personal experience with either of the RAID-modes.

But my understanding is that a RAID 5 can be more complicated to set up.

And RAID 5 will have dataloss if 2 HDD's fail.

RAID 0+1 could still be fine even with 2 HDD failiures, depending on which HDD's fail.

[s4iko1337]

@sn0le thx for reply

but when 2 hdd's fail, you must have been a lot of unhappy :D

[s4iko1337]

@s4iko1337 oh and a very important difference is that raid 5 has increased read speed but writing speed is as slow as with 1 hdd.

raid 1+0 has increased reading and writing speed

[sn0le]

@s4iko1337:

Thats very true. :)

And anyways. Like I did mention in my RAID introduction video, RAID doesn't replace the need for backup.

You should always have a separate backup of the data you wan't to protect.

And if you have that backup, it won't matter if all the drives are lost, because you'll have a complete backup of the data.

If a lightningstrike fries your computer that has the RAID, it might not matter what kind of RAID you were using. :)

[MrZero761]

Excellent explanation, Well done, You actually made it a lot clearer to me

Thanks

[sn0le]

@MrZero761:

Glad to hear that. :)

[atomicfart3514]

Very well done! This helped me greatly in understanding RAID5. The one thing I still don't understand well is how write speeds compare to a standalone hard drive.

[sn0le]

R/W-speeds will be higher than a single drive.

Just look at my latest video, where I compare a single Seagate 1TB vs 3 Seagate 1TB in RAID0.

RAID5 would probably not be as fast as RAID0, because of the generating of paritybits.

And also, the R/W-speed will vary, depending on the filesize and the stripesize.

So with RAID5 you basically have to tweak the stripesize to match the "average" filesize of what you work with.

I will run RAID1 myself.

Not enough experience to fiddle with RAID5.

[BeeefyBeast]

Is there a raid that would work this way:

2 hard drives(500GB each)

250GB of drive #1 will be used like in raid 0 with the 250GB of drive #2

so now there is 250GB left on each drive which could be used to back-up eachother. is there such raid array?

[sn0le]

@BeeefyBeast:

Hmmm.

I am not sure. Wouldn't it just be better to do a mirror of those 2 drives? (RAID1).

You would get less speed than a RAID0, but you'd have redundancy, which RAID0 doesn't offer you.

[saiprakash1]

excellent work SNOLE really liked teh videos u posted , really helpful , i m going to show this video to my teacher and will have it displayed to the entire class...

THANKS 1ce AGAIN

[sn0le]

@saiprakash1:

Thanks. :)

[merlock18]

So its not literally 4 bits and 4 bits? I thought it was... Are you possibly gonig to make a video about raid-z? or raid-z2?

[sn0le]

@merlock18:

Yeah, it is not literally 4 and 4 bits.

I just simplified it.

When you set up a RAID-5 you can use default strip size, or you can tweak it to the size that gives you the best performance for your need.

If you choose a size that's too small, you get loss of performance.

If you set a size tha'is too big, you can suffer from "storage penalty".

That means HD-space gets wasted.

Strip size also affects seek time.

With RAID-5 you definetly need to know what you're doing.

I don't. Hehe.

[SciTech09]

Excellent job in explaining the details of RAID. Thanks.

[sn0le]

You're welcome.

I am by no means an expert.

But tried to research and make a video that is (hopefully) easy to understand.

:D