SATA-II explained

[Monstermunch]

Smids.....

Any chance of speaking on MSN at some point, just need to go through a few technical q's for you about setting up raid0?

 

[meansizzler]

I'm a bit confused, will standard SATA cables support the full SATA2 Speed if you have them set up in raid, I was under the impression that you need SATA 2 cables, which can handle that amount of speed, like the Silverstone SATA 2 cables...

http://www.silverstonetek.com/products-cp01.htm

 

[smids]

I'm a bit confused, will standard SATA cables support the full SATA2 Speed if you have them set up in raid, I was under the impression that you need SATA 2 cables, which can handle that amount of speed, like the Silverstone SATA 2 cables...

http://www.silverstonetek.com/products-cp01.htm

Marketing nonsense - a SATA cable will provide full speed - 150 or 300MB/s.

 

[meansizzler]

Marketing nonsense - a SATA cable will provide full speed - 150 or 300MB/s.

yes but thats what happened with USB 1 and USB 2.0 cables, USB 1.0 cables could not handle the bandwidth of usb 2.0 speeds.., is it not the same wiht SATA cables?..

 

[smids]

yes but thats what happened with USB 1 and USB 2.0 cables, USB 1.0 cables could not handle the bandwidth of usb 2.0 speeds.., is it not the same wiht SATA cables?..

Nope - SATA cables are just simply that. I'm sure there is a maximum bandwidth somewhere, but for now, it copes easily.

 

[Fatfish]

Hey smids - great thread. I've never understood what SATA drives and RAID arrays were for or how they worked - you've adequately explained both. Thanks very much.

However, I would just like to clarify something as I'm putting together a spec for my new system - if RAID arrays are prone to failure (and I'm thinking in context of RAID 1+0 here), what's the benefit over having two identical SATA drives and just regularly backing up all your data to the second drive periodically (apart of course for the up to the second mirroring of your main drive that the RAID array would offer)?

For instance, I am putting together a spec for my new system. I've never used SATA drives or RAID arrays before. Should I buy (for example) 2 x 160Gb SATAII drives (mobo does support SATAII 3Gb/s) and set them up in RAID 1+0 array or should I have them as independent drives and just back my data from drive 1 up on to drive 2 every week (obviously not including the OS which needs to be installed should there be a corruption)? Would I achieve any kind of benefit (such as performance) by setting them up in RAID 1+0?

Thinking about it, would the backup drive still be read if your main drive dies and is replaced with a new drive and a reinstall of XP?.

Or on the other hand, would using just a single SATA drive be more appropriate for my usage - which would be primarily gaming and internet, as well as storing my media. On my current system, I'm using a 160Gb IDE drive and this appears to offer ample space requirements for now. I would probably look to port this over to the new system as well rather than selling it - would that be possible with a SATA RAID 1+0 array running?

Again, thanks very much for the help.

 

[smids]

I can see your understanding of the various RAID levels is flawed .

http://www.acnc.com/04_01_00.html for more info. Use the bar at the top to look at various RAID levels.

In short: you are looking at RAID0, RAID1 and RAID1+0 (let's stick to RAID 0+1 for now, RAID 1+0 is also known as RAID 10 and is a bit more complex).

RAID0 - 2 drives minimum, 1/2 data on each drive therefore almost doubling reads (will never actually be double, more like 150-160% of one drive speed) and writes because more data can be read and written at the same time. Very unreliable - one drive fails, the array fails = all data lost. Total space sum of all drive capacities.

RAID1 - 2 drives minimum. Data is written to 2 drives. Excellent reliability - if one drive fails, you automatically run from the good drive and then the array may be rebuilt when the duff drive is RMA'ed etc. High cost as 2 drives = 1 drive storage space. I.e. drive storage = total drive capacities divided by 2.

RAID0+1 - 4 drives minimum required. A RAID0 array which is mirrored. i.e like 2 parallel RAID0 arrays. Can survive one drive failure without loss of data and 2 drives if one array completely fails i.e. you are left with one RAID0 array still running. Drive capacity = total drive capacity divided by 2. Benefits of RAID0 speed with RAID1 reliability but high cost of 4 drives.

RAID1 is useful for data backup BUT if one drive corrupts, i.e. virus, this is mirrored to the second drive! Yes, not a great thing to happen.

If you have a normal backup drive i.e. XP+ data drive (HDU1) where the data is backed up to HDU2, HDU2 will function with any installation of new OS's etc. It is an independent disk entirely (don't format it obviously when installing on the other HDU! ). So in answer to your question, yes it will still be read.

Porting a current installation is possible. I would use something like Acronis True Image 9 Home which is what I use - it is excellent and much more reliable than something like Norton Ghost 10 or 9 when dealing with RAID arrays.

Hope this helps - let me know if you have any more questions.

 

[Fatfish]

Yes, that does help......a lot! I had read right through your thread and thought I'd grasped it, but perhaps not as well as I'd thought. I had wondered how you could achieve RAID 0+1 with only 2 drives - my mistake!!

So what's the realistic reliability of using RAID arrays then? Are they more prone to failing than running just single HDD's as independent/individual drives? I understand the potential benefit of having a 1.5-1.6 x faster drive access or mirrored data for backup (or both for that matter), but not if the system used has a greater likelihood of failing - or again, am I missing something here?

Lastly, considering what I will be using it for, will running a RAID array improve the performance of my system - with regard to gaming and media (ripping mp3's, video playback etc) - or would I be better off keeping my drives independent and just backing up the data I do want to keep regularly? And for me, performance gain means performance gain - not 0.02ms increase in write speed or something like that. I mean, will it improve say mp3 ripping by 10 seconds per track for example? I guess I'm looking for a tangible method of measuring the improvement to decide if it's worth the hassle.

And thanks again for your help.

 

[smids]

Reliability is entirely the reliability of the individual drives. If a drive fails, it fails, nothing can be done. All you have to consider is probability.

1 drive, chance of failure = 1
2 drives, chance is doubled - 2 drives same time
etc. As you can see, the chance of a disk failing increases with more drives. Simplistic, I know but it does hold true relatively.

Ripping mp3's - entirely processor dependent.
Loading game maps/unraring files, raring files, installing things, loading windows, running large apps, loading games will all be faster on a RAID0.

RAID 1 increases read by about 5%, but writes will be approximately halved as the controller has to make sure data is exact on both drives. Writes - installing things, unraring, writing video files e.g. directly recording from a DV camera. Writes are less important really.

You would only see a realistic increase with RAID0 but unless you have a good backup solution, it's not a great idea.

My setup:

RAID0 2x 80GB hitachi SATA-II - Windows/Games/Programs
RAID1 2x 80GB Hitachi SATA-II - Irreplaceable data - music , pictures, documents, backup of the entire RAID0 every week (Acronis compresses data so it can fit on this drive - uses about 30GB roughly on a normal usage RAID0 array with some games installed including Steam).
320GB Storage drive - storage but can be replaced - annoying to lose but I wouldn't lose sleep over it. Video files, data I don't care about etc (though these are put onto a DVD if I want to keep them for sure)

 

[Fatfish]

Ok, that makes sense, thanks. Sorry, when I said ripping mp3's, I meant the time to read and write the files to disk - but thinking about it, it makes little odds because (as you say), it's relying on the cpu to process it, which the HDD should easily keep up with. Penny. Dropped.

I like the way you've got your drives set up. Very logical and sensible. So if I was to purcahse 4 x 80Gb SATAII drives, I could arrange the same arrays as you have there - one for performance, one for security and one for non-essential mass storage. Would I be right in saying that I could use my current 160Gb IDE drive as the storage drive alongside the SATAII drives (arrayed).

So if one of your SATA drives with Windows on failed, what would be involved in getting your system running again? And would that drive(s) then need to be RMA'd?

 

[smids]

Ok, that makes sense, thanks. Sorry, when I said ripping mp3's, I meant the time to read and write the files to disk - but thinking about it, it makes little odds because (as you say), it's relying on the cpu to process it, which the HDD should easily keep up with. Penny. Dropped.

I like the way you've got your drives set up. Very logical and sensible. So if I was to purcahse 4 x 80Gb SATAII drives, I could arrange the same arrays as you have there - one for performance, one for security and one for non-essential mass storage. Would I be right in saying that I could use my current 160Gb IDE drive as the storage drive alongside the SATAII drives (arrayed).

So if one of your SATA drives with Windows on failed, what would be involved in getting your system running again? And would that drive(s) then need to be RMA'd?

Oh, just literally copying? That would be 160% faster because of the RAID0. All read and writes on a RAID0 are faster - any encoding would limit ripping which is what I thought you meant . Writing and reading from a disk uses very little CPU and the CPU is ridiculously faster than an HDU at processing data. Think 20GB/s bandwidth of the L1 cache and about 6GB/s L2 cache (as this is what would be used for the processing of data numbers) compared with about 60MB/s for an HDU. It's the HDU that slows everything down!

My array seems logical - to the untrained eye - but is quite illogical! Watch this:

One RAID1 drive fails - easy, replace.
One RAID0 fails - not so easy. Either don't use the computer and use my laptop (like now - comp is being completely rebuilt with new mobo/RAM/PSU/improved watercooling) OR, more likely, cause a failure of the RAID1 - i.e. steal a drive and then restore the RAID0. The new drive would then slot into the RAID1 which could be rebuilt at a later date. If the other RAID1 drive failed in between and I lost everything, well then it's my fault!

 

[Fatfish]

So if the array with the OS failed (RAID 0), you can nick one of the essential data drives (RAID 1) and slot it into the RAID 0 array. Rebuild the drive and off you go, without the RAID 1 being accessible until you've had a new drive delivered and can replace and rebuild it - (with the obvious issue of the remaining RAID 1 disk failing in the meantime and losing all your essential stuff still a possibility).

But you're saying if the RAID 0 fails, there's a high likelihood that it could kill the RAID 1 array aswell? Why is that? Surely it shouldn't affect the RAID 1 array - it's just a fault with the RAID 0 and a seperate array/disk? So in theory then, the failure of the RAID 0 would negate the benefit of the security of the RAID 1 if it increases the chance of the RAID 1 array also failing when the RAID 0 one does. Surely that's a really silly way of doing it......oh! Ah, I think I see what the problem with your setup is now!

So the only safe way to do it is to use RAID 0+1 and have all your OS/Programs/Games & esssential data kept together on the one fast Raid 0 array and mirrored using RAID 1, or by having both arrays set to RAID 1 - which would be slow and painful, but safer. Am I right in saying that both these methods give you a total of 160Gb storage space (assuming 4 x 80Gb drives are used)?

**edit: hold on, no - the RAID 0+1 would only give you 80Gb with the 4 drives. The RAID 0 would provide the 80Gb space over 2 drives, while the RAID 1 then mirrors this using both drives. So only 80Gb in total for the price of 4 drives. Yes?**

It does sound like RAID arrays may not be the best choice for me because of cost and poor reliability. I may as well just buy 2 x SATA 80Gb drives and back up regularly, with my 160Gb IDE as non-essential mass storage that doesn't require backing up.

My last question - and this doesn't necessarily relate to RAID arrays - if you use 2 x SATA(or II) drives and perform two tasks, with each task involving data from one drive (i.e. mp3 playing from one drive and video clip playing from the other), would it perform this task more efficiently than if all the data was stored on the one physical drive?

I know I've asked a lot and thanks very much for the help. Basically trying to decide whether RAID arrays are the way forward for me. Bet you wish you'd never replied now!!

 

[smids]

So if the array with the OS failed (RAID 0), you can nick one of the essential data drives (RAID 1) and slot it into the RAID 0 array. Rebuild the drive and off you go, without the RAID 1 being accessible until you've had a new drive delivered and can replace and rebuild it - (with the obvious issue of the remaining RAID 1 disk failing in the meantime and losing all your essential stuff still a possibility).

But you're saying if the RAID 0 fails, there's a high likelihood that it could kill the RAID 1 array aswell? Why is that? Surely it shouldn't affect the RAID 1 array - it's just a fault with the RAID 0 and a seperate array/disk? So in theory then, the failure of the RAID 0 would negate the benefit of the security of the RAID 1 if it increases the chance of the RAID 1 array also failing when the RAID 0 one does. Surely that's a really silly way of doing it......oh! Ah, I think I see what the problem with your setup is now!

So the only safe way to do it is to use RAID 0+1 and have all your OS/Programs/Games & esssential data kept together on the one fast Raid 0 array and mirrored using RAID 1, or by having both arrays set to RAID 1 - which would be slow and painful, but safer. Am I right in saying that both these methods give you a total of 160Gb storage space (assuming 4 x 80Gb drives are used)?

So why don't you have everything on the one 160Gb RAID 0+1? Surely it provides the same storage, but with better performance and security overall?

Would the RAID 0+1 still provide better performance than just using the SATAII drives independently (i.e. not in RAID array)?

My last question - and this doesn't necessarily relate to RAID arrays - if you use 2 x SATA(or II) drives and perform two tasks, with each task involving data from one drive (i.e. mp3 playing from one drive and video clip playing from the other), would it perform this task more efficiently than if all the data was stored on the one physical drive?

I know I've asked a lot and thanks very much for the help. Basically trying to decide whether RAID arrays are the way forward for me. Bet you wish you'd never replied now!!

Not quite - I steal a drive from my RAID1 meaning the RAID1 is now degraded but fully functioning. RAID1 can continue to be used even with a failed drive so it reduces the RAID1 to a normal disk. This becomes a RAID1 again as soon as a new disk arrives. This would be about 7 days of unsecured data. Of course, I don't have to do that, I could just use my laptop but I'm impatient. I very much doubt 2 drives would fail at the same time - the probability is extremely low hence the reason I feel happy about doing that. The two arrays are independent but the way I have it setup makes their paths cross.

I used to have a RAID0+1 but I wanted faster writes - RAID0+1 means writes are no faster than a single drive - RAID0 makes it 160%, then RAID1 virtually halves this so net it doesn't gain any write speed and may lose a tiny amount. Plus a RAID1 is ever so slightly more secure than a RAID0+1 - we're talking minute percentages here...

160GB = 4x80 RAID0+1 and yes it is better performing than independent disks.

160% reads (actually it's more like 175-180% thinking about it!)
100% writes relative to a single drive.
100% more reliable
But also louder - 4 drives seeking and working at the same time .

Last question: yes, two drives independently being accessed is more efficient and faster.

 

[Fatfish]

Ok, thanks. That makes sense. Not as bad as I thought then. But does the failing RAID 0 array increase the likelihood of the RAID 1 array failing as well - or have I misunderstood that part?

No rush for tonight as I'm off to bed, but tomorrow would be good if you have time. Cheers mate and good night!

 

[smids]

Ok, thanks. That makes sense. Not as bad as I thought then. But does the failing RAID 0 array increase the likelihood of the RAID 1 array failing as well - or have I misunderstood that part?

No rush for tonight as I'm off to bed, but tomorrow would be good if you have time. Cheers mate and good night!

No, the RAID0 is completely independent of the RAID1. It's only because I take one of the RAID1 drives that it is more likely to fail - but this is not because I have taken a drive, it is because drives can fail at any time, so there is no more likelyhood of the remaining RAID1 drive failing as there was before I stole the 2nd drive. I hope that isn't too long for this hour ! I could leave the RAID1 alone and it remains completely unaffected by the RAID0 failure. It's not as bad as you think. I've never actually had an HDU failure as yet, so it's all theory for me. Considering I have 5 HDU's in total, this is good going.

 

[Fatfish]

Morning mate - I'm back for more!

Brain just reached meltdown last night I think. Spent half an hour in bed trying to get to sleep - and all I could think of was ways to build my system using RAID arrays! Sad, I know!

Ok - that sounds a little more promising than I had thought. Perhaps it was the lateness of the hour, but I'd read your original post to mean that failure of the first array would increase likelihood of failure of the second. So your setups not that bad then - only really becomes an issue if you steal the drive from the RAID 1 array, and even then it's only a higher theoretical likelihood of losing the remaining info because you're then only using 1 drive instead of 2. Ok, I understand now.

So, could I set the arrays up like this:

RAID1 2 x 80Gb = Windows & essential data (e.g. music, photos etc.)
RAID0 2 x 80Gb = Programs and Games
160GB IDE storage drive = non essential data.

This way would provide greater security and stability by having the OS and essential data mirrored with RAID 1 (so if one drive fails, you can still run from the second drive and rebuild at a later date without needing to steal a drive from the RAID 0 array) and still have the benefit of having your programs and games running on the faster RAID 0 array - no biggie if this fails as you can either replace the drive and rebuild or reformat remaining drive as independent drive and reinstall required programs.

Downside to this is I'd only have 80Gb storage for my essential data and Windows, but it would at least be more secure in case of disk failure - but as you've pointed out, if the remaining RAID1 disk was to also fail then I would lose all of the essential data and OS. But that's fairly unlikely, and at least it would provide some additional security over having just a single independant disk.

Would having Windows running on a RAID1 array cause it to take longer when shutting down as well - as it would need to write to disk before powering down? And what about performing tasks or using Windows applications - would this also be noticeably slower? I'm assuming boot up shouldn't really be affected too much as it only reads ~5% slower than normal.

Can you see any other downsides to having a setup like this?

And finally - using your original setup - if the RAID0 array failed and you couldn't afford or wait to replace the faulty drive, could you not just reformat the remaining working drive and reinstall Windows and your programs on to the one drive and boot from that? Leaving the RAID1 array intact. So it won't be as fast as it was, but it will still work - yes?

 

[smids]

Yep, you understand my array now - guess you were a bit tired .

With your suggested setup - windows wouldn't run any differently from a single hard drive, only with half speed writes and about 5% increased read. Shutting down wouldn't take long. Really, it takes a lot to saturate 30mb/s writes. You probably won't even notice it until you, say, install something. Writing something to disk is quick anyway, and really only noticable if you do video editing where you need the speed and those types of application.

Can't see any downdsides reallyto your suggested setup. You might want to put essential programs on the windows drive so that if the RAID0 does go down, you can still perform essential tasks so things like Firefox/MS Office/ CD writing software all should really be with windows and non-essential programs like..umm...Divx or Realplayer could be on the RAID0.

About my setup - yes, using the backup image on my RAID1, I could just run a single drive yes - I hadn't thought of that! To quote Family Guy Episode 'Petarded': http://www.youtube.com/watch?v=7c53N0LK_es You are 'Peter' the fat guy who is the main character (green trousers, white shirt) - I am the doctor at the instutute. Watch the clip up to 00:45 seconds - yes, that's how I feel at the moment (the doctor's reaction).

 

[Fatfish]

Damn work PC and it's lack of Java plug-ins!! Will have to wait until I get home to view it. Family guy ***! Funniest program I've seen in years - bar a few of Homer's better moments!

Glad I could be of help - I do have my moments. Few and far betweeen though so might be worth bookmarking the thread for posterity!

And I see what you mean about the essential programs being kept on the RAID1 as well. As we said though, the only problem with it is the reduced amount of storage space for the essential data - unless of course I buy 2 x 120Gb or even 2 x 160Gb drives and have them setup in RAID1. It's just the additional cost to justify it.

Thanks again for your help smids. Cheers.

edit: Sorry, I've just read one other thing that I'm not sure about. Some people are saying that the Gigabyte DS3 Conroe mobo won't allow booting from a RAID array - they seem to think it will be fixed in a BIOS update. Are most mobo's like this, or is it just a one off with this one?

 

[Fatfish]

@ mods - why was my '***' abbreviation removed? I know it's a bit geeky, but it was only said tongue in cheek - and was only meant as quick way of saying that I thought it was a great program?!

I'm only asking so I don't make the same mistake twice!

edit: ok, so it's done automatically - hence it having wiped it from my query as well. It only means 'for the win'. It's not exactly rude or unacceptable language though! This place is like Orwell's 1984 - they are watching us!

 

[Dave]

This is a bit of a daft question. I am looking into Socket A motherboards at the moment - particularly the nForce 2. It has SATA on it, and I was wondering - if I bought a new hard drive from Overclockers will it work on nForce2?

I take it that the hard drive will given that SATA2 is backwards compatible, but I'd like to make sure