Topic: RAID1 Bug

[Duncan Drury]

This is in regards to the bug at:

http://www.e-smith.org/bugs/index.php3?op=showBug&bugID=40

which doesn't show up under the regular list of bugs as far as I can see.

To cut a long story short, SME Server will only allow you to see half your hard drive capacity when using RAID1 (ie two 40Gb hard drives will only show up as 19Gb hard drive when mirrored by RAID).

I am having this problem, and have followed the work around, but it hasn't worked.  Anyone got any ideas?

Dunx

[Duncan Drury]

Could this have anything to do with both drives being on the same IDE cable?  Do they both need to be master on their own IDE channel?

[Brian]

You need to use Raid 0 if you want to double your storage.  Raid 1 is acting exactly as it should.

[Charlie Brady]

Duncan Drury wrote:

> To cut a long story short, SME Server will only allow you to
> see half your hard drive capacity when using RAID1 ..

That's only true for versions 5.x (and only sometimes then).

Charlie

[Kelvin]

Hi Duncan,

Charlie wrote :
>...  only sometimes then).

I concur, which is why my preference is to use hardware based RAID - more beneficial especially if the server is to be in a work / production environment where downtime can be inconvenient and possibly even costly.

Brian wrote :
>Raid 1 is acting exactly as it should.

Based on the information of Duncan's post, this is incorrect. RAID 1 does not half the capacity of the individual drives (using 2x 40GB drives which should give one 40GB Mirrored set).

Kelvin

[Charlie Brady]

Kelvin wrote:

> I concur, which is why my preference is to use hardware based
> RAID - more beneficial especially if the server is to be in a
> work / production environment where downtime can be
> inconvenient and possibly even costly.

Some "hardware" raid will actually increase downtime, because after you replace a failed drive, you can't get past the BIOS until the raid pair is rebuilt.  So choose carefully.

Downtime with built-in software RAID shouldn't be more than a few minutes.

Charlie

[Kelvin]

Charlie Wrote :

>you can't get past the BIOS until the raid pair is rebuilt. So choose carefully.

Again, I concur - although navigating the BIOS is usually easier than remembering RAID recovery commands for us non-gurus in a pinch.

My preference is for OS independent Hardware RAID subsystems like the Accusys systems. It gives you an audible alaram on failure with indicator lights to show which drive has failed. It also allows hot swapping of the failed drive eliminating the need to power off the system to replace the failed drive. After replacing with a suitable drive, rebuilds are automatic (with battery backups within the unit to track rebuild state in case the server is shut down intentionally or otherwise before rebuild is complete).

OS independence mean no OS drivers are required (as long as the OS recognises and works with the motherboard IDE controller) to drive the unit. Therefore, it avoids the problems with kernel upgrades, etc. which can break support for cards whose drivers are not part of a standard distribution / kernel tree.

Kelvin