RAID 1 and other thoughts

[Box Brownie]

Hi All

I am doing a 'review' of my next build and there have been many discussions about backup strategies.

So I just wanted to see if this makes sense???

The build I am planning is for an SFF using an mATX board with a case that can take 3 or 4 HDDs inboard so one of the possible uses as RAID 1 is available is to use two of the HDDs in RAID1 as well as backing up as I do now to external HDD(s).

Does anyone routinely use that method as their primary 'backup' against disk failure?

:)

[Ephemeral]

I use a 3 disk RAID 5 system as my data drive, and back up to an external HD that I take to work as off site backup. I still can only afford to lose a maximum of 1 drive, but I get the benefit of more storage space.

[Box Brownie]

Thanks for the insight.

The reason for two HDDs in RAID1 is that I would use the 4th HDD as my primary scratch disk in both editing environments.

I am also finding it a real challenge to get mATX boards that will take an Intel CPU - I am limited to the G33 chipset or the nVidia GeForce 7100/nForce 630i where as what would be great is the Intel P35.

Any experience of the G33 and nVidia GeForce 7100/nForce 630i for use in photo or NLE video work?

:)

[David Saunders II]

I use a 3 disk RAID 5 system as my data drive, and back up to an external HD that I take to work as off site backup. I still can only afford to lose a maximum of 1 drive, but I get the benefit of more storage space.

Note that many of the newer RAID controllers, including those from 3Ware (my preferred brand) also support RAID 6. RAID 6 is exactly like RAID 5 but with a built-in hot spare enabling you to lose 2 drives without data loss.

[CyberDyneSystems]

RAID 1 is the simplest and most reliable "RAID" per disk, easiest to re-build and easiest to migrate.

I use it absolutely in any machine where Data is important.

As you seem to understand, it is not a back up solution, a second (or more) method is required, but in the meantime it does mean that a catastrophic disk failure will not lose any recent work, nor will it impede you from continuing to work until such time as you can make a second mirror to replace the lost disk.

One of it's biggest advantages is that nothing "weird" is done to your data. You have two complete copies of the data on two physical drives that any PC can read. No striping, parity or funny business, no proprietary rebuild of the array needed relying on a specific controller to get your data back, it's just there on the two drives.

I believe this is the only RAID that offers this simplicity.

It costs a little in $ per MB than some other RAID, but if a two to four disk RAID is all you intend to use, at todays HD prices, it's still a nice solution. And with the cost of a RAID 5 controller to contend with Vs. an onboard controller for free,...

On a larger scale, RAID 5 and 6 have definite advantages, eventually the speed boost is really amazing too, and you lose fewer of your GB to parity,. but cost can be higher to get started. Not all Mobo RAID controllers have RAID5, and you can't do it with two disks.. and it's almost not worth it to do RAID 5 with three IMHO. Seek times can be even slower than a singe drive ( a lot slower depending on controller, where as RAID 1 boosts seek times and random access)

IMHO for RAID protecting on the cheap, RAID 1 is a simple elegant affordable solution, and as most MOBO's support it, the cost of entry is merely two drives (these days less than $200.00 easily)

[Baadil]

RAID 1 is great.

RAID 6 is buggy and slow.

[David Saunders II]

RAID 1 is great.

RAID 6 is buggy and slow.

RAID 1 mirrors data. RAID 6 is exactly the same as RAID 5 (striping with parity) except with a spare drive. RAID 5/6 is also faster than RAID 1, especially when used with duplexing (i.e. multiple controllers) and 10s of thousands of companies use RAID 5/6. This is because when you read to or write from 3+ disks, the speed increases since you have the independent I/O and the random seek time of read/write heads of each drive to deliver the data. It is neither buggy nor slow. This is a perfectly viable option and anyone who knows that they're talking about will agree.

Your above claim is ignorant, over-generalized at best, does not offer evidence to back it up and is in actually just plain wrong.

[orisky]

What kind of speed impact is there with Raid 1 since it's writing to two drives each time?

[CyberDyneSystems]

RAID 1 actually improves the read speed over a single drive, as it does not wait to find the data on both drives, only one,. so the seek times can be faster with two drives to chose from.

In writing, the impact is minimal, only noticeable usually via a benchmark, not "perceptible" .. but it depends on the controller, ... a lot.
Some on board motherboard's on board controller may be more likely to show a speed hit than others. Most hardware based cards on the pother hand will not show an impact at all.

ie: I would not let it worry you.

[CyberDyneSystems]

RAID 1 mirrors data. RAID 6 is exactly the same as RAID 5 (striping with parity) except with a spare drive. RAID 5/6 is also faster than RAID 1, especially when used with duplexing (i.e. multiple controllers) and 10s of thousands of companies use RAID 5/6. This is because when you read to or write from 3+ disks, the speed increases since you have the independent I/O and the random seek time of read/write heads of each drive to deliver the data. It is neither buggy nor slow. This is a perfectly viable option and anyone who knows that they're talking about will agree.

Your above claim is ignorant, over-generalized at best, does not offer evidence to back it up and is in actually just plain wrong.

The only thing I would mention that may be slightly contradictory to your assessment is the following:

It depends heavily on the controller.
Now with RAID 6 I don't think any of the low cost options even exist yet? (I could be wrong) but there are now a good many motherboards with low cost on board chips offering RAID 5, but it is usually a pretty poor alternative to the real solid hardware based RAID 5 found on your $500.00-$1k 3-ware or Areca boards..
In RAID 5, the low budget software RAID controller invokes a much larger impact on performance (and arguably reliability) than the same low budget controller would impact a RAID 1 array.
We even see a HUGE difference even in relatively simple RAID 0 speeds when going from many of the budget controllers to a real hardware based card.

In short, though any good add on card with a RAID 5 (or 6) array should out pace a RAID1 in most cases, the same is not true when the controller is an on board low budget one. Ive seen benchmarks where the RAID 5 array on such controllers brings the entire disk subsystems performance crawling to it's knees.. as working out the parity in a write creates latency.

Likewise in simply working out striping on a RAID 0 array these same low budget controllers tend to offer only a fraction of the speed increase vs a single drive when compared to what the hardware controller can do when striping data.

This is again why I mention RAID 1 as being more simple,. a controller can be pretty "dumb" and still get RAID 1 right, as all it has to do is allow the same data to be written to two drives, there is nothing to calculate, create, split up or spread out.

Either Parity, or Striping require more "balls" then simply writing the data to two drives,. with RAID 5/6 you need both, and thus to really get the best from 5/6 you need a ballsy controller.

[gef]

Raid1. One of my disks corrupted and I was able to rebuild it from the good copy. That made be very happy to have my photos stored on a raid volume....

[Grentz]

I like RAID 1. I run 2x RAID 1 arrays on my file server one of which has a hotspare (the one my pictures are on). Right now it is pretty small as one array is 36gb and one is 9gb, but they are all SCSI so the drives cost a lot.


10s of thousands of companies use RAID 5/6. This is because when you read to or write from 3+ disks, the speed increases since you have the independent I/O and the random seek time of read/write heads of each drive to deliver the data.

Its also because they can get more storage space from fewer total drives than with RAID 1. But the fact still remains that it is easier to build and maintain a RAID 1 array because degradation over time can effect a RAID 5/6 array quite a bit and it is much harder to restore the data from a failed RAID 5/6 array onto a different machine with a different controller if you cannot find the one you originall used.

[CyberDyneSystems]

Not to mention that fact that when you factor in the cost of a good robust RAID5/6 controller and enough drives to do it (3 drives minimum) your costs are at frist much higher than the cost of two drives on a low cost controller.

As a RAID 5 scales, it eventually becomes more cost effective on a per MB basis, but that's only if you actually are scaling your storage needs high enough for that cost effectiveness to even kick in. Right now there is no RAID5/6 option anywhere that could be as affordable as a 500GB or TB RAID 1 set up. Because we can use two affordable drives with an affordable controller, comparing RAID1 to 5/6 is really almost apples and oranges since we can use such affordable and small amounts of gear.

[Andy_T]

Good thoughts here.

Am currently also considering to move from a 1-HD + backup DVD solution (most forum members' hairs will be raised by now) to a RAID solution in the 500 GB range.

Does anyone here have experience with a Buffalo Drivestation Quattro, a 4-disk/1TB total system that is very affordable at EUR 380 ($ 600) and seems to offer quite a bit of data protection with Raid 1 and 5 supported?

There's also the cheaper Drivestation Duo, that features 2x 500 GB drives with RAID 0/1.

Best regards,
Andy