[K12OSN] Software RAID-1 with 3 Disks?

[Krsnendu dasa]

2008/8/11 Terrell Prude' Jr. <microman at cmosnetworks.com>

> Onatawahtaw wrote:
>
>> Greetings,
>>
>> I also am researching the issue of RAID. I am wondering if it is possible
>> to setup RAID-1 across 3 Disks. From what I've read I've heard some people
>> say that it is not possible. That Raid 1 requires pairs of disks, but that a
>> third could be used as a hot spare. However, other people are claiming to be
>> using RAID-1 with 3 Disks. Is this possible?
>>
>>
>
> Yep, but only with one of the disks as a hot spare.  A RAID 1 is by
> definition a mirror involving two disks.
>
I have heard someone (Les Mikesell?) mirroring onto 3 drives, with the third
a usb removable drive. He then takes the third drive elsewhere as a backup.
So it is possible. Writes are done to all three drives. Reads from the
fastest drive. This way two drives can fail and the show still goes on.

>
>
>  Also, I'm trying to understand exactly what a hot spare is. From what I am
>> understanding so far, a hot spare starts out empty. If one of the two disks
>> in a RAID-1 configuration becomes corrupted, the good disk then starts
>> copying itself to the hot spare. It then uses the hot spare as its mirror.
>> Is this a correct understanding of it?
>>
>> Thanks,
>>
>> -Kevin
>>
>>
> Yep, that's how hot spares work.
>
> --TP
>
>
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