Hardware RAID 1 and 9.04

[luggw1]

I'm looking to build a machine that incorporates a hardware RAID 1 configuration on two HDDs using a dual boot of 9.04 32 Bit and Win XP. Is there any trouble that I should anticipate in doing this? Any special preparations I should make prior to starting the process? This is my first venture into the world of RAID.

Thanks.
Bill Lugg

[dibl]

Re: Hardware RAID 1 and 9.04

Hardware RAID using a motherboard SATA chip is not the same for Linux as it is for Windows. The big difference being, the RAID chip OEMs don't write drivers for Linux, in general. Your consumer motherboard with a RAID chip (Silicon Image or VIA or Promise or whatever) will not work in Linux, because there is no driver. Besides which, upon examination, these low-cost SATA-based RAID setups turn out to be BIOS/software-driven, not real "hardware" RAID after all.

Start studying here:

http://linuxmafia.com/faq/Hardware/sata.html

Here's the key information, about 3/4 down the page:

RAID issues (a separate wrinkle): (link)

Most ATA RAID host adapters (except 3Ware Escalade, Adaptec 24x0, Areca, HP/Compaq, IBM ServeRAID, Intel SRC*/ICP Vortex, LSI Logic MegaRAID 150-4/150-6, and Tekram) turn out, upon examination, to not be real hardware RAID, but rather software/BIOS-dependent fakeraid. (I.e., missing hardware functionality is traditionally emulated inside idiosyncratic, undocumented, and proprietary software drivers, to hit low price points). Fakeraid is difficult to support in Linux — absent either reverse-engineering, special proprietary drivers, or (rare) manufacturer cooperation. (HighPoint, LSI Logic, Nvidia, Promise, and VIA provide proprietary drivers to support their respective fakeraids. I personally would steer clear.)

Linux often cannot read existing fakeraid volumes on such host adapters, unless you're willing to use proprietary fakeraid drivers (where available). But unless you're dual-booting MS-Windows, you shouldn't care, because Linux's software RAID (kernel "md" driver) is much faster and more reliable. You're advised to blow away fakeraid volumes, use SATA drives as straight block devices, and enable Linux software RAID instead, during Linux installation.

Kernel coders are slowly figuring out some fakeraid variants, and coding ataraid/dmraid modules.
Warning about media errors and RAID

Be aware that if any one drive of your SATA-based RAID array goes offline for any reason, including a significant string of media errors, depending on the SATA host adapter, the array may hang and need to be rebooted. This is because many SATA host adapters, like ATA generally absent special hardware provisions, simply don't support hotplug functionality.

This is known to be true, in particular, of Intel's ICH5/ICH5-R series, and Garzik has pointed out that that chip series, plus Intel ICH6 (in non-AHCI mode), Pacific Digital Talon, and Promise SATA SX4 — at minimum — will never support hotplug.

Here's a respectable vendor of Linux-supported RAID controller hardware:

http://www.3ware.com/3ware_home.htm

Please post your results here -- I'm sure many will be interested to hear how you fare.

[Telengard]

Re: Hardware RAID 1 and 9.04

http://linuxmafia.com/faq/Hardware/sata.html

The information at that link is a bit difficult for me to digest, but I think I get the gist of it. It sounds like motherboard RAID features simply don't work under Linux.

More specifically, I guess I can give up on my plans to use the RAID 1 (mirroring) feature of this motherboard. Am I right?

[dibl]

Re: Hardware RAID 1 and 9.04

I guess I can give up on my plans to use the RAID 1 (mirroring) feature of this motherboard. Am I right?

You can give up using the RAID chip on the motherboard to do it. However, Linux "dm" raid is still available to you, and should work as well on that motherboard as any other.

[luggw1]

Re: Hardware RAID 1 and 9.04

After doing some homework, I determined that I can't do the software RAID approach in my case because I need to dual boot between Windoze and Kubuntu. So, I am currently waiting for a 3ware hardware RAID card to do the job for me. I found one for $125 which looks like it will do the job for me.

At any rate, if you're going straight Linux the software RAID approach is just the ticket, but if you've got to dual boot, true hardware RAID is the only option. I haven't found any mobos that will support it. They all seem to use fakeRAID instead.

HTH
Bill Lugg

[Telengard]

Re: Hardware RAID 1 and 9.04

It looks like I'll need a card if I want RAID. Thank you very much.

[luggw1]

Re: Hardware RAID 1 and 9.04

Take a look at https://www.ewiz.com/detail.php?name=3WA80062LP. That's the one I bought, but haven't received yet. The company has been good to deal with.

HTH
Bill Lugg

[Telengard]

Re: Hardware RAID 1 and 9.04

Now I have been given reason to hope that the RAID 1 function of my motherboard might work.

Intel ICH* RAID configurations are fakeraid but are supported by Linux. My understanding is that Linux will see a mirror but not a striped volume on an ICH* chipset.