SI SATA Raid
Aleksandar Milivojevic
amilivojevic at pbl.ca
Tue Nov 23 22:05:59 UTC 2004
Rob wrote:
> I just installed FC3 and it detects my SI SATA controller and drives
> but it does not see the Raid0 set I have created (4x160GB), it just
> see four individual drives. ANy suggestions? Is this even supported?
I'm not 100% sure (more around 10% sure) about this (not much experience
with SATA). But from what I saw so far, SATA RAID built into the
chipsets for standard PC motherboards usually means "software raid that
you can define from BIOS". OS sees those drives separately, and needs
special set of drivers. When you have drivers installed individual
disks are hidden from you, and you only see RAID devices. RAID is
handled by the driver (sofware RAID), not by the hardware. If you
turned off that RAID support in BIOS, and simply build RAID devices
using mdadm, you would end up with basically the same thing. Former by
using special unstable and still under development drivers, later by
using standard and stable Linux md drivers.
The only two real differences I see are:
1. You don't need special drivers if you turn RAID support off in BIOS.
This is an argument towards not using chipset/BIOS RAID support, and
using normal Linux software RAID tools (mdadm). MD drivers are very
stable, and easy to use. Definetly argument for going this route.
2. If you have more than one OS installed (say Windows and Linux), and
you want to have Windows partition on RAID kind of device, and you want
it to be visible from Linux, going BIOS way is the only way you can go.
Said that, I also found that device mapper with help of some additional
packages might be able to handle those software RAIDs defined from BIOS.
Seems to be chipset dependent (not all chipsets supported). Last time
I checked, support was read-only. In other words, whatever changes in
status of RAID device was detected by the OS, they don't get recorded
into RAID configuration (for example, if one disk in RAID-1 goes south
and is totally out of sync). Next time you boot, your OS dosn't know
anything about it. I wouldn't call this actually usable.
--
Aleksandar Milivojevic <amilivojevic at pbl.ca> Pollard Banknote Limited
Systems Administrator 1499 Buffalo Place
Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
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