zfs discuss - Oct 2009 - raidz "ZFS Best Practices" wiki inconsistency

<http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#RAID-Z_Configuration_Requirements_and_Recommendations>
says that the number of disks in a RAIDZ should be (N+P) with
N = {2,4,8} and P = {1,2}.

But if you go down the page just a little further to the thumper
configuration examples, none of the 3 examples follow this recommendation!

I will have 10 disks to put into a RAIDZ.  I would like as little
"waste"
as possible, so that means just 1 hot spare, and a 3,3,3 config for the
remaining 9 is not appealing.  Should I do a single 9 disk RAIDZ, per
the guideline, or should I do 4,5.

This is for engineering data.  My workload isn''t established yet but
from
talking to the guys the "working set" would fit in a TB and just be
local
to engineer workstations, while the file server will just store
infrequently used data. As such, I''m inclined to do a single 9 disk
RAIDZ and maximize the available disk space, which at the same time
follows the configuration guideline.

I''m pretty sure I already know the correct answer as I remember when
this guideline was created and why.

Besides just thinking out loud, I do want to emphasize the inconsistency
on the wiki and suggest that it be updated or a comment added.

-frank

Thanks for your comments, Frank.

I will take a look at the inconsistencies.

Cindy

On 10/22/09 08:29, Frank Cusack wrote:
>
<http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#RAID-Z_Configuration_Requirements_and_Recommendations>
> 
> says that the number of disks in a RAIDZ should be (N+P) with
> N = {2,4,8} and P = {1,2}.
> 
> But if you go down the page just a little further to the thumper
> configuration examples, none of the 3 examples follow this recommendation!
> 
> I will have 10 disks to put into a RAIDZ.  I would like as little
"waste"
> as possible, so that means just 1 hot spare, and a 3,3,3 config for the
> remaining 9 is not appealing.  Should I do a single 9 disk RAIDZ, per
> the guideline, or should I do 4,5.
> 
> This is for engineering data.  My workload isn''t established yet
but from
> talking to the guys the "working set" would fit in a TB and just
be local
> to engineer workstations, while the file server will just store
> infrequently used data. As such, I''m inclined to do a single 9
disk
> RAIDZ and maximize the available disk space, which at the same time
> follows the configuration guideline.
> 
> I''m pretty sure I already know the correct answer as I remember
when
> this guideline was created and why.
> 
> Besides just thinking out loud, I do want to emphasize the inconsistency
> on the wiki and suggest that it be updated or a comment added.
> 
> -frank
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