Theoretical - Raid in one drive.

[piemadd]

Since we all know that you can make partitions and put drives in raid. Since SAS hard drives can read and write at the same time, couldn't you make a partition and put both in raid for maybe faster performance. If we can get this big enough, maybe Linus could make a vid on it. Who know if it will work.

What do you think?

[Tedster]

Since we all know that you can make partitions and put drives in raid. Since SAS hard drives can read and write at the same time, couldn't you make a partition and put both in raid for maybe faster performance. If we can get this big enough, maybe Linus could make a vid on it. Who know if it will work.

What do you think?

I don't think that this is a good idea, with RAID 0 if you're reading from one partition, you're reading from all partitions. And the same for writing. Being able to read and write at the same time doesn't get you anywhere in this case.

[Naeaes]

Nope. You're right about them being able to read and write simultaneously but you'd need them to be able to read and read or write and write simultaneously for RAID to work. You know?

[piemadd]

I don't think that this is a good idea, with RAID 0 if you're reading from one partition, you're reading from all partitions. And the same for writing. Being able to read and write at the same time doesn't get you anywhere in this case.

I meant raid 2. It fills up each partition a little and it can have the capabilities of 2 saga drives in raid. It could fool the computer if the partition was done on one computer and the raid 2 setup was made on another(by transferring the drive between the computers).

[Sack]

Since we all know that you can make partitions and put drives in raid. Since SAS hard drives can read and write at the same time, couldn't you make a partition and put both in raid for maybe faster performance. If we can get this big enough, maybe Linus could make a vid on it. Who know if it will work.

What do you think?

Raid uses two drives to read from, combining the data into one. Being able to write at the same time doesn't help you at all...

[piemadd]

Nope. You're right about them being able to read and write simultaneously but you'd need them to be able to read and read or write and write simultaneously for RAID to work. You know?

One SAS cord is as powerful as 2 SATA cords. It should theoretically work.

[Philcat101]

The thing that makes RAID fast is that there are 2 separate drives with their own controller, each pushing at their speeds.

If you do that, it is dividing the controller's job in two, then putting the performance back together, and only risk losing data to corrupted partitions.

[Tedster]

One SAS cord is as powerful as 2 SATA cords. It should theoretically work.

I thought it was four, and that doesn't get you anywhere..?

[Godlygamer23]

One SAS cord is as powerful as 2 SATA cords. It should theoretically work.

The hardware does not. The head is constantly re-positioning itself in that regard - you will not be getting improved performance by putting two partitions into RAID 0.

[piemadd]

Raid uses two drives to read from, combining the data into one. Being able to write at the same time doesn't help you at all...

Remember, we are putting 2 partitions in raid.

[alpenwasser]

If we're talking HDDs: The speed is limited (among other things) by how quickly the read/write heads can move across the platters to the needed location. So if you made two partitions and then created a RAID0 from those, the heads would actually need to move between the two partitions in order to write the striped data:

 

* move to partition 0, write first part of stripe 0* move to partition 1, write second part of stripe 0* move to partition 0, write first part of stripe 1* move to partition 1, write second part of stripe 1,* etc.

So you would actually most likely be slower instead of faster because the heads need to move much more.

Now, maybe the disk would try to optimize that and write the stripes from partition 0 first, but then you'd have the issue that if you get a power failure before the disk moves to partition 1 and writes all the stripe parts into that, all your data whose parts are so far only in partition 0 would be lost because you only have half of it.

Basically what you end up doing is manually fragmenting your data across your disk.

SSDs:

Assuming it's not the interface which is your bottleneck, the controller would probably be next on that list. It's not just magically going to be able to process double the amount of data.

[Sack]

One SAS cord is as powerful as 2 SATA cords. It should theoretically work.

No you're still wrong, you still cannot read from two places in one go...

[piemadd]

The hardware does not. The head is constantly re-positioning itself in that regard - you will not be getting improved performance by putting two partitions into RAID 0.

Wow. A mod replying to my topic. Well then I gues my plan to get a topic in a video is stopped.

[piemadd]

If we're talking HDDs: The speed is limited (among other things) by how quickly the read/write heads can move across the platters to the needed location. So if you made two partitions and then created a RAID0 from those, the heads would actually need to move between the two partitions in order to write the striped data: 

* move to partition 0, write first part of stripe 0* move to partition 1, write second part of stripe 0* move to partition 0, write first part of stripe 1* move to partition 1, write second part of stripe 1,* etc.

So you would actually most likely be slower instead of faster because the heads need to move much more.Now, maybe the disk would try to optimize that and write the stripes from partition 0 first, but then you'd have the issue that if you get a power failure before the disk moves to partition 1 and writes all the stripe parts into that, all your data whose parts are so far only in partition 0 would be lost because you only have half of it.Basically what you end up doing is manually fragmenting your data across your disk.SSDs:Assuming it's not the interface which is your bottleneck, the controller would probably be next on that list. It's not just magically going to be able to process double the amount of data.

Now we're onto something. Maybe we could try to make each partition go on half of the disks(there are 4-6 disks in a hard drive). It could be optimized as 2 2-3 disk hard drives in raid.

[Tedster]

Now we're onto something. Maybe we could try to make each partition go on half of the disks(there are 4-6 disks in a hard drive). It could be optimized as 2 2-3 disk hard drives in raid.

What?

[Sack]

Wow. A mod replying to my topic. Well then I gues my plan to get a topic in a video is stopped.

Well you just showed that you don't understand how partitions works, drives work or RAID work.

 

Edit: add physics as well to the list above.

[Philcat101]

Wow. A mod replying to my topic. Well then I gues my plan to get a topic in a video is stopped.

You know, they talked about this in the WAN show, it is not a new idea.

 

The problem where your plan is bad is that the 2 drive controllers controlling 2 separate storage mediums is what makes RAID fast: Adding the controllers' speed.

What you are doing is taking 1 drive and controller, dividing the drive, making it harder to read, and still putting the same stress on one controller, resulting in the same and even slower speeds: Dividing the drive and adding it back together for instability.

[alpenwasser]

One SAS cord is as powerful as 2 SATA cords. It should theoretically work.

I thought it was four, and that doesn't get you anywhere..?

Yeah, SFF-8087 to SATA breakout cables are pretty common:

 

But it's basically just a connector aggregator, you connect a single drive to each endpoint.

 

You can also get them with SAS endpoints:

 

There are of course other variants, but just to give you an idea.

 

The connector on the single end is a SFF-8087, but that's just for connecting to the controller, I'm not aware of any drives which use that.

Wow. A mod replying to my topic. Well then I gues my plan to get a topic in a video is stopped.

We don't really determine what Linus puts in his videos. His Youtube conglomerate is quite separate from us moderators, we're basically just community volunteers, but we don't really have influence on what videos he does or does not make.

Now we're onto something. Maybe we could try to make each partition go on half of the disks(there are 4-6 disks in a hard drive). It could be optimized as 2 2-3 disk hard drives in raid.

The problem is that the read/write heads move as a single assembly, not each one for each platter separately:

 

[Godlygamer23]

 We don't really determine what Linus puts in his videos. His Youtube conglomerate is quite separate from us moderators, we're basically just community volunteers, but we don't really have influence on what videos he does or does not make.

Correct. User suggestions are just as valid as our suggestions.

[alpenwasser]

Since we're on the internals of how HDDs work, this video gives you a bit of a better idea:

Despite the HDD being huge and old, the fundamentals aren't really much different from today's drives.

Also, this link might be of interest:

http://www.eassos.com/how-to/partition-table-001.php

[piemadd]

Correct. User suggestions are just as valid as our suggestions.

Ok. I just thought if tons of people were to get Linus' attention, he might think of making a video on it.

[TheRandomness]

Ok. I just thought if tons of people were to get Linus' attention, he might think of making a video on it.

He wouldn't make a video on something that's currently impossible. For your idea to work properly, the head would have to be in two places at once.

[piemadd]

He wouldn't make a video on something that's currently impossible. For your idea to work properly, the head would have to be in two places at once.

You know. There are multiple heads(2 per disk). I do know that they go at the same time, but they will be reading bits in the same area on the disks.

[Blade of Grass]

You know. There are multiple heads(2 per disk). I do know that they go at the same time, but they will be reading bits in the same area on the disks.

But hard drives already spread out data accross the platters to speed up reading and writing, what you want to accomplish is already handled at a firmware level by the hard drive.

[Captain_WD]

~snip~

 

Hey there Implosivetech,

 

Creating a RAID array on a single drive is quite impractical for a few main reasons:

 - In order for any RAID to actually give you benefit, it should either give you redundancy or speed. Having a RAID array on a single drive can't possibly give you any of those. There can't be redundancy of the data as if the drive fails, you would lose everything on it, not only part of the data. Speed gain is also something that can't be done since the data needs to be written at least on two places at once and this is impossible as the drive has only one actuator with a read/write head per platter.

 - Creating a drive with multiple read/write heads is impractical as you need the mechanics for more moving parts, more actuators hence more space, heat and noise output and power consumption which would both increase the cost the drive beyond reasonable values and add way too much complexity to the drive which on its own would lead to much higher failure rates and risk for the data.

 - No matter what you do the read/write head on each platter can function at one place at a time. To have an actual speed increase you would need a second one (like in Striped arrays) to perform the same as the first one. 

 

Feel free to ask if you happen to have questions

 

Captain_WD.