Re: What is the point of RAID?
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>---- Original Message ----
>From: lee@yun.yagibdah.de
>To: debian-user@lists.debian.org
>Subject: Re: What is the point of RAID?
>Date: Wed, 12 Nov 2008 02:44:46 -0600
>
>>On Tue, 11 Nov 2008 19:54:11 -0600
>>Mark Allums <mark@allums.com> wrote:
>>
>>> that three drives is 50% more likely to fail than two. More than
>>> fifty percent, if I remember my statistics at all correctly.
>>
>>Do you mean it is more likely that any one drive in the array fails
>when
>>you have more drives, or do you mean that it is more likely for a
>drive
>>in the array to fail when you have more drives? If drives fail more
>>often when being used in an array with more drives, what makes them
>>fail more often under those conditions?
>>
>>> If you
>>> have a RAID 50 running on 20 SAS drives and 4 hot spares, you
>better
>>> buy quite a few for cold spares, you are going to lose a drive
>every
>>> two months. At least.
>>
>>You are saying that the age of the drives doesn't matter at all?
>Then if
>>you lose one drive out of 24 every month, that would mean that about
>4%
>>of all drives sold are junk. The new ones you get could fail within
>the
>>first few minutes ... or not work at all. Or does this mean that it
>>takes about one to two months before you find out if a new drive is
>>junk? And why don't the drives that are junk fail in the first few
>>minutes or don't don't work at all?
>>
>>
The conventional wisdom for hardware is called "infant mortality".
Most hardware failures occur during the first hundred or so hours of
operation. This is why good vendors typically burn the devices at
the end of manufacturing prior to shipment.
Larry
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