[ale] XFS on Linux - Is it ready for prime time?

[Jim Kinney]

On Thu, Apr 22, 2010 at 2:42 PM, Greg Clifton <gccfof5 at gmail.com> wrote:

> Hey, I'm not great with math, but if you have one hot spare for each active
> spare, wouldn't you need mirrored quadruplets?
>

Um. Yes. My math is  better than my language. The triplet is composed of 2
active and one hot spare drive. In new math, that is 3 drives. In old math
it's also 3 drives.

But I like Greg Freemyers do real triplets with a single hot spare for the
array. With that setup I can lose _ANY_ 2 drives and not lose data. Recovery
time for live mirrors is is on the order of ns where n is number of live
mirror partners and s is write speed under load. For raid 5 its more like
ns/t where n is surviving drive count, s is write under load and t is total
number of drives in array.

>
> On Thu, Apr 22, 2010 at 2:26 PM, Jim Kinney <jim.kinney at gmail.com> wrote:
>
>> RAID 5 was an invention for a time when hard drives were total crap tons
>> of money. The pain of losing a drive in a RAID 5 array is just no longer
>> balanced by the cost of the drives. If a 1TB drive is only $100, it's
>> bluntly dirt cheap now to have a hot spare in a 4 active drive RAID 10
>> system. The recovery is much easier and faster when checksums don't have to
>> be calculated for every stinking block on the drive(s).
>>
>> My ideal rig: Striped array for speed composed of mirrored triplets - 2
>> active, one hot spare per active pair.
>>
>>
>> On Thu, Apr 22, 2010 at 1:05 PM, Greg Clifton <gccfof5 at gmail.com> wrote:
>>
>>> Shift in focus to the hardware side of the equation. This thread
>>> concentrates on software generated corruption issues, but I have some
>>> hardware related questions. First, with RAIDed hard drives, are any file
>>> systems more or less likely to cause (or minimize) the likelihood of
>>> corruption of the array and if so, why? Second Greg F (and others) have
>>> commented on NOT using RAID 5 (and RAID 6) esp. with large hard drives.
>>> Looks like 1 or 2 TB hard drives will soon be "standard issue" for
>>> everything but notebook computers. So does that mean that RAID should be
>>> considered 'dead,' except for 0, 1, 10? Third, would SSDs solve the failure
>>> from bad sector issues with HDDs and thus be safe for RAID 5/6
>>> implementations?
>>>
>>>
>>>
>>> On Thu, Apr 22, 2010 at 9:41 AM, Ed Cashin <ecashin at noserose.net> wrote:
>>>
>>>> On Wed, Apr 21, 2010 at 9:34 PM, Doug McNash <dmcnash at charter.net>
>>>> wrote:
>>>> ...
>>>> > Does anyone out there use xfs? How about a suggestion for a stable
>>>> replacement.
>>>>
>>>> If you use the xfs in the mainline kernel, it's a crap shoot because
>>>> of the amount of churn in the code, but
>>>> if you use a long-term kernel like 2.6.16.y, 2.6.27.y, or the kernels
>>>> maintained by distros, then it ought to be stable (as long as the
>>>> distro has enough of a user base for other people to find the xfs
>>>> bugs first).
>>>>
>>>> --
>>>>  Ed Cashin <ecashin at noserose.net>
>>>>  http://noserose.net/e/
>>>>  http://www.coraid.com/
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>>>
>>>
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>>
>>
>> --
>> --
>> James P. Kinney III
>> Actively in pursuit of Life, Liberty and Happiness
>>
>>
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>
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>


-- 
-- 
James P. Kinney III
Actively in pursuit of Life, Liberty and Happiness
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