From mboxrd@z Thu Jan  1 00:00:00 1970
From: Phil Turmel <philip@turmel.org>
Subject: Re: best base / worst case RAID 5,6 write speeds
Date: Tue, 15 Dec 2015 14:52:39 -0500
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To: Dallas Clement <dallas.a.clement@gmail.com>
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On 12/15/2015 02:44 PM, Dallas Clement wrote:

> Wow!  Thanks a ton Phil.  This is incredibly helpful!  It looks like I
> need to do some experimenting with smaller chunk sizes.  Just one more
> question:  what stripe cache size do you recommend for this system?
> It has 8 GB of RAM, but can't use all of it for RAID as this NAS needs
> to run multiple applications.  I understand that in the >= 4.1 kernels
> the stripe cache grows dynamically.

I don't really know.  I use the default 256, but all of my parity raid
arrays have 16k chunks and are relatively lightly loaded.  Consider
sampling stripe_cache_active once a second for a normal workday on real
workloads to figure out what you need.

Phil