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Re: relationship of nested stripe sizes, was: Question regarding XFS on

To: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
Subject: Re: relationship of nested stripe sizes, was: Question regarding XFS on LVM over hardware RAID.
From: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Date: Sat, 01 Feb 2014 12:47:31 -0600
Cc: xfs <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <7A732267-B34F-4286-9B49-3AF8767C0B89@xxxxxxxxxxxxxxxxx>
References: <7A732267-B34F-4286-9B49-3AF8767C0B89@xxxxxxxxxxxxxxxxx>
Reply-to: stan@xxxxxxxxxxxxxxxxx
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On 1/31/2014 12:35 AM, Chris Murphy wrote:
> Hopefully this is an acceptable way to avoid thread jacking, by
> renaming the  subject…
> 
> On Jan 30, 2014, at 10:58 PM, Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
> wrote:
>> 
>> RAID60 is a nested RAID level just like RAID10 and RAID50.  It is
>> a stripe, or RAID0, across multiple primary array types, RAID6 in
>> this case.  The stripe width of each 'inner' RAID6 becomes the
>> stripe unit of the 'outer' RAID0 array:
>> 
>> RAID6 geometry        128KB * 12 = 1536KB RAID0 geometry  1536KB * 3  =
>> 4608KB
> 
> My question is on this particular point. If this were hardware raid6,
> but I wanted to then stripe using md raid0, using the numbers above
> would I choose a raid0 chunk size of 1536KB? How critical is this
> value for, e.g. only large streaming read/write workloads? If it were
> smaller, say 256KB or even 32KB, would there be a significant
> performance consequence?

You say 'if it were smaller...256/32KB'.  What is "it" referencing?

-- 
Stan

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