Hard drives

[bassfisher6522]

This is a hypothetical question.

How do you make two independent hard drives of the same make, model and volume act as one hard drive?

 

[Dwarf]

By having them in an array (RAID/JBOD).

 

[bassfisher6522]

Thanks. Next question; do we have a tutorial on this?

 

[whs]

Have a look at this: How to Create a Software RAID Array in Windows 7 - How-To Geek

 

[bassfisher6522]

Thanks for that link. What it is the difference between spanned and Raid 0. I've done some googleing but can't find anything definitive. Are they one and the same?

 

[whs]

Here is one definition I found:

A spanned volume is made up of disk space on more than one physical disk. It is used to combine free space on different hard disk drives installed in a computer in order to create a large logical volume. It can be created on dynamic disks only. It supports two to thirty-two disk drives. A spanned volume is not fault tolerant and cannot be mirrored or striped.

That implies that it is not the same as Raid0 (striped) or Raid 5 (mirrored)

 

[Dwarf]

Let's imagine that you have a 2 drawer filing cabinet and are writing a series of letters which will be filed in various ways in this cabinet. The drawers represent the drives, and the letters the data files.

Initially, the drawers are completely separate and are independant of one another. Letters may be stored in either one without complications.

Now, let's link the drawers together to form one big drawer. There are 3 main ways that this can be done: RAID0, RAID1, and JBOD.
Let's look at these in order.

Firstly, RAID0. This combines the capacity of the drawers giving an overall capacity of twice that of the smallest drawer. Letters are stored here by being split - odd pages going in the first drawer and even pages in the second. Loss of one of the drawers here results in the effective loss of all of the letters.

Secondly, RAID1. With this analogy, a complete copy of the letter is stored in both drawers, the total effective capacity of which is that of the smallest drawer. Loss of one of the drawers has no detrimental effect on the letters, as both contained a complete copy.

Thirdly, JBOD. Here the drawers can be of different sizes, and the capacity is the sum of that of the individual drawers. Letters are stored in a sequential format, beginning with the first drawer. When that drawer is full, letters are then stored in the second drawer. There are several outcomes here following the loss of a drawer. Obviously, letters stored in that drawer will be lost, but the fate of the others can vary. Depending on circumstances, you may or may not be able to retrieve letters from the remaining drawer.

 

[DeaconFrost]

Color me jaded, but there's very little reason to ever consider RAID0. You won't see the performance benefits that are present in theory, and most often, those who claim to see the performance boost are using synthetic benchmarks, or "just feel like it's faster". It was a fad, and it was debunked and put to bed a few years ago. SSDs may be a little different, but at the same time, the same rules apply...if one SSD is unreliable and fails...you lose your data on both.

 

[Dwarf]

Point noted and taken. However, I should point out that I have and still am using RAID0 on my system and was doing so on my previous system without any issues whatsoever. It all depends on your hardware.

 

[DeaconFrost]

It all depends on your hardware.

It depends little on hardware and mostly on your luck, and how much risk you are willing to take for percieved (not actual) performance gains. My main point is...it was debunked and put to bed years ago, with Anandtech's article still being considered the final word, aka the nail in the coffin. If anyone wants to still run RAID0 on their own, so be it, but I truly think people need to stop short of suggesting or recommending it.

 

[whs]

Color me jaded, but there's very little reason to ever consider RAID0. You won't see the performance benefits that are present in theory, and most often, those who claim to see the performance boost are using synthetic benchmarks, or "just feel like it's faster". It was a fad, and it was debunked and put to bed a few years ago. SSDs may be a little different, but at the same time, the same rules apply...if one SSD is unreliable and fails...you lose your data on both.

I agree except when you want the mirroring of Raid5. On SSDs (if only used for the OS) Raid0 makes no sense at all because it does not improve the access time by one iota. That will be different once we can afford large SSDs for massive files.

I remember one case though were Raid0 on the SSD seemed to make sense. The OP bought two 30GB SSDs in lieu of one 60GB SSD because the two were cheaper. Then he threw them together with Raid0.

 

[DeaconFrost]

I love RAID5, and have it running on several servers at work, and one at home. I think RAID5 certainly has it's place...my main and only beef is with RAID0. I understand the point between turning two cheap 30 GB SSDs into one 60 GB, but now your data is twice at risk, and given the unreliability of SSDs...that would scare me.

 

[whs]

and given the unreliability of SSDs

Deacon, from where do you get that idea? In over one year I never had a problem - neither with OCZ nor with Intel. And in any case, imaging is your friend.

 

[DeaconFrost]

Deacon, from where do you get that idea? In over one year I never had a problem - neither with OCZ nor with Intel. And in any case, imaging is your friend.

Just because you have one that has lasted a year, doesn't mean everyone has the same experience. It should go without saying that one person's experience doesn't make for the entire industry. The knock from the very beginning on SSDs was that they are unreliable and have a finite amount of reads/writes. Have they improved...sure, but not to the level of mechanical drives as of yet.

 

[whs]

I guess it is not worth discussing it any further.

 

[DeaconFrost]

I'm open to discussion, but I'm also battle-scarred from so many forums in which a person disputes an industry-held belief using only their lone individual experience. The knock against an SSD has always been that they are not yet as reliable as mechanical drives. You seemed surprised by this, like I was pulling information out of my rectum. If I wanted to go solely on personal experience, I bought 10 SSDs for work laptops, and 4 of them failed within the first week of usage. But I don't ever argue or debate on personal experiences, because mine may or may not be typical of what everyone else sees.

 

[whs]

I'm open to discussion, but I'm also battle-scarred from so many forums in which a person disputes an industry-held belief using only their lone individual experience. The knock against an SSD has always been that they are not yet as reliable as mechanical drives. You seemed surprised by this, like I was pulling information out of my rectum. If I wanted to go solely on personal experience, I bought 10 SSDs for work laptops, and 4 of them failed within the first week of usage. But I don't ever argue or debate on personal experiences, because mine may or may not be typical of what everyone else sees.

I understand what you are saying. Personal experience is not a statistical average. But I am following the SSD scence very closely (since about 2 years) and I have not seen any such complaints in recent times.
I don't know how many SSDs you have installed, but the three I have (and I am just buying a 4th) have never given me any trouble - but maybe that proves nothing.

 

[DeaconFrost]

I wish I could say the same, personally speaking, but most of the write-ups I've read comparing SSD vs HDD specifically mention the reliability issues, and the finite lifecycle of them.

The one I am using personally in my laptop that you helped my get working is running like a champ. That's what led me to upgrade 10 of my company's laptops. I looked a bit foolish when 4 of the 10 died that quickly.

 

[whs]

There is a lot of hype about the lifetime cycle. But then, how long do you keep these devices. I think they will hold up for 3 or 4 years after that it is anyhow time to buy somthing new. For now I have seen more people with failing HDDs than SSDs. But that may be because they are so recent and have fewer users.

 

[DeaconFrost]

There are still a lot of variables to consider. I don't think we'll know for another two years or so which type drive is truly the most reliable. I've had HDDs fail in these laptops, so it will be telling to see how SSDs fair in the same systems, getting used the same, with the same power on/off cycles.