Re: RAID Help!!

From: André von Raison (avr_at_ix.heise.de)
Date: 01/19/05 

Date: Wed, 19 Jan 2005 11:50:37 +0100

frank schrieb:
> Deke wrote:
>
>> 1. How does one recover from software RAID (mirroring). Meaning .. if
>> the primary drive that the PC boots from fails, how do you tell it to
>> automatically boot from the secondary drive. Assume that I am using
>> adaptec scsi and the boot drive is ID 0 and secondary mirror drive is
>> ID 1.
>>
>> 2. Any one know of any good external rackable 1U SCSI->RAID enclosures
>> that has good value and is reliable and is not too pricey? With
>> controllers included please..
>
> IF you really had RAID 0 - mirroring going, just unplug the bad drive.
> If it does not boot, you didn't have Raid 0 working. For Hardware
> Raid you need to set a new drive in & config.

Just to be correct: the RAID level for mirroring is RAID 1. RAID 0 is
striping which means that if one drive of the stripe set fails you loose
all your data on that stripe set.

> There is also a difference if it was Hardware Raid or software raid.

Thats correct, but if Deke would have a hardware RAID he would have
gotten an error message but his system would be still useable/bootable.
So I assume he's using a software RAID. Ideally (if he has configured
his system using disk labels) he just has to unplug the broken disk to
get his system back to life-without the RAID on the boot device. In the
second step he should edit his grub.conf to change the boot device from
/dev/sda to /dev/sdb power down the system, put in the replacement for
the defective disk, reboot, partition and configure the new disk to act
as mirror for /dev/sdb. The driver should the recognize the
inconsistency of the RAID and start a rebuild of the mirror.

HTH

Andre 

-- 
Andre von Raison

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