[ale] RAID, IDE and/or Linux

[Jeff Hubbs]

That's been my understanding - a RAID 5 filesystem with a drive out is 
still intact for read and for write, but it's performance is degraded 
and will remain so until the bad drive is replaced and its contents 
rebuilt.  

- Jeff

David Corbin wrote:

> I think Jeff's point was that failover *is* instaneous.  But you're 
> right that for sometime afterward, performance is "below par".
>
>
> Chris Ricker wrote:
>
>> On Sat, 16 Feb 2002, Jeff Hubbs wrote:
>>
>>> Chris Ricker wrote:
>>>
>>>> On Sat, 16 Feb 2002, Jeff Hubbs wrote:
>>>>
>>>>> The downside to RAID 1 here is the 1:2 effective/actual capacity 
>>>>> ratio, i.e., takes 40GB to make 20.  If he goes RAID 5 instead and 
>>>>> the three-drive medium, he gets a ~2:3 ratio - takes 60GB to get 40. 
>>>>
>>>> But loses instantaneous fallover....
>>>>
>>> Since when??
>>>
>>
>> Since always.  By definition, with RAID-5, you don't have a live copy of
>> data like with RAID-1 -- you have dispersed parity bits from which 
>> data can
>> be slowly reconstructed.  Even when you have hot spare(s) (and I hope if
>> you're using RAID-5 that you do), you still have to wait for the new 
>> drive
>> to be rebuilt from the parity on the remaining disks.  Until the new 
>> drive
>> finishes rebuilding, you run in a degraded mode where data is 
>> reconstructed,
>> not live.
>>
>> later,
>> chris
>>
>>
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>
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