a different approach to WHS OS mirroring

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benogil

Limp Gawd
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Sep 28, 2006
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Just in case anyone else is interested in mirroring their OS drive without wasting too much drive space, I may have found a solution to this. When I first bought all the hardware, I decided to go with this external HD enclosure for the mirrored OS drives. For one thing, my motherboard didn't have RAID built in (so I would have had to buy an adapter card anyway), and I had read so many warnings against RAID & WHS that I decided that if I went with an external RAID enclosure that connected via eSATA, I'd be guaranteed that it would be 100% hardware RAID and WHS wouldn't know any different (since it's connection was eSATA, that prevents any RAID via software on the host). But as it turned out, that enclosure has another feature besides simple RAID0 and RAID1, it also has SAFE33 and SAFE50. Essentially, it takes either 33% or 50% (depending on which one you choose) of each drive and creates a hardware mirror out of them, then the remaining space is spanned as a single large volume. So WHS sees my two 1TB drives as two drives: a 333GB one, and a 1.33TB one. The former being a mirror of two 333GB partitions on the two drives, and the latter being a span of the remainder of the space on those two drives. It then takes the 333GB volume and splits it between a 20GB system partition and a 313GB primary data partition, and I'm still left with the 1.33TB "drive" to add to the pool. So in this scenario, I've only "spent" 333GB on mirroring, but it actually ends up being cheaper than using two small drives for the OS mirror and a larger drive for the pool, due to the relatively high $/GB of small drives. The only catch is that you have to have an eSATA port that supports port multiplication with FIS switching for the system to be able to see both volumes over the single eSATA link.
 
sounds sort of like RAID 5 with 2 drives.... interesting although if the controller dies, your screwed...
 
What benogil is pointing out here is a great idea.

When you do the SAFE33 or SAFE50, the safe portion is fully mirrored and not dependent on the controller.
So, if the enclosure dies and you can find a replacement or a drive dies, the SAFE portion is protected and will be accessible in any system.

The non-SAFE portion is what you will lose.

If you use WHS, I would allocate the non-SAFE portion to duplication if you have duplication turned on some of your shares.

Another option would be to look for an SATA controller with the SAFE feature (if there are any).
 
I like this idea. Maybe when I do a rebuild of my box I'll look into this.
 
You can essentially do the same without sacrificing performance on any mobo with an ICH7 + chipset.
 
spectrumbx said:
You mean, ICH7 or higher by default support SAFE mode? :confused:

From all my readings, this is a Silicone Image chipset (most notably Sil5744) feature only: http://www.tomshardware.com/reviews/silicon-image-brings-virtualization-esata,1610-4.html.
Click to expand...

Its not called SAFE mode.....thats just marketing BS ;)

What it really is a matrix.

It uses the same concept that Intel Matrix Raid uses.
When you enter the RAID utility on an Intel Mobo and setup a RAID1 or RAID0 or RAID5 you specify what size to make the RAID Volume.

So if you wanted "SAFE33" and had two 1tb drives
You make a 333GB RAID1, and dont touch the rest.
Then install windows to your 333GB RAID1 drive.
Instal Matrix Raid Console make simple volumes with the rest of your two drives.

http://www.intel.com/design/chipsets/matrixstorage_sb.htm
 
I wouldn't call it BS marketing, but cool on the Intel Matrix RAID features.

Looking at this image:
matrix-RAID_4drives_2005.jpg


Do you know if there is a way to show the non-RAID'ed portion of each drive as its own independent partition?
 
TheSpoon said:
Linux's software RAID can do this too, right?
Click to expand...

Sure.
You can do that in Windows too using dynamic disks.
However, you can't install WHS on software RAID volume. :)

This is about creating hardware RAID volumes in a flexible fashion.

As drives are getting larger and larger, it is a waste to use two large drives mirrored just for the OS.
Using a portion of those drives for the OS and reclaiming the rest for other use is what is being proposed here.
 
This is not partition based.

No one has mentioned a partition, and you can use any FS you wish.
 
Other than the fact that this is hardware-based and therefore allows you to install any OS you wish, I don't see how it's conceptually any different from what you can do with Linux's software RAID/LVM. I understand that this method doesn't require you to create partitions beforehand, but the end result seems to me to be the same.
 
TheSpoon said:
Other than the fact that this is hardware-based and therefore allows you to install any OS you wish, I don't see how it's conceptually any different from what you can do with Linux's software RAID/LVM. I understand that this method doesn't require you to create partitions beforehand, but the end result seems to me to be the same.
Click to expand...

There has always been a richer choice in the software world in regard to RAID.
That we know.

It is finding similar options in hardware RAID that is being discussed.
So, being able to install the OS on the RAID is everything for this discussion. :)
 
spectrumbx said:
There has always been a richer choice in the software world in regard to RAID.
That we know.
Click to expand...

I didn't know that :p
I'm clearly no expert. My intent was merely to understand whether this is something that could be achieved with Linux's software RAID (which I've used only once to set up a RAID-1 mirror).
 
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