Raid 6 would mean you'd have to lose at least two drives to be wiped out.
Raid 6 with hot spare means you'd have to lose at least three drives,
Kind of like, which is better:
Raid 5 with a hot spare, or
Raid 6 with no hot spare
Either way, you'd have to lose two drives to be fried. I would think that
Raid 6 would be better if there was a risk the second drive would be lost
while the hot spare for raid 5 was becoming active and still rebuilding.
With Raid 5 you lose the space of one drive to striping (spread out across
all drives). How much do you lose to Raid 6?
Is there a performance degradation from removing one of your disk drives
of a 8 drive SCSI raid set to become hot spare?
I would think there would be two performance hits. One, dropping from 8
drives supporting the raid stripe down to only 4. The other performance
hit would be one less disk arm assisting while it's just sitting there
waiting to be hot spare.
IBM Certified System Administrator - IBM i 6.1
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
Kendallville, IN 46755
From: Sue Baker <sue.baker@xxxxxxxxxx>
Date: 03/19/2014 06:34 PM
Subject: Re: RAID 6 rebuild time - can I slash it?
Sent by: midrange-l-bounces@xxxxxxxxxxxx
Jeff Crosby <jlcrosby@xxxxxxxxxxxxxxxx> wrote on Wed, 19 Mar
2014 16:29:52 GMT:
On a Saturday of my choosing, our HW service provider is going
to take our System i 520 from 2 8-drive RAID 5 sets to 2
8-drive RAID 6 sets w/hot spare.
Wow! This is quite a change in data protection.
You realize that in order to have your data at risk, you need to
lose 2 drives in the RAID6 array?
Generally, I recommend to customers to do RAID5 + hot spare or
RAID6. I see it as more importante to have as many disk units
as possible for RAID6 versus adding the tiny bit of reduced
delay time for rebuild to begin on a single failed drive that is
provided by hot spare.
Time to create the RAID6 arrays is mostly dependent on the size
of the drives. Other factors are whether there is data on them
or not (% full is irrelevent) and the type of disk controller.
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