ZFS - thanks

[Tonix (Antonio Nati)]

Patrick M. Hausen ha scritto:
> Hello,
>
> On Thu, Jul 09, 2009 at 09:17:35AM -0300, Nenhum_de_Nos wrote:
>
>   
>>> So now we have this setup:
>>>
>>> 	NAME               STATE     READ WRITE CKSUM
>>> 	zfs                ONLINE       0     0     0
>>> 	  raidz2           ONLINE       0     0     0
>>> 	    label/disk100  ONLINE       0     0     0
>>> 	    label/disk101  ONLINE       0     0     0
>>> 	    label/disk102  ONLINE       0     0     0
>>> 	    label/disk103  ONLINE       0     0     0
>>> 	    label/disk104  ONLINE       0     0     0
>>> 	    label/disk105  ONLINE       0     0     0
>>> 	  raidz2           ONLINE       0     0     0
>>> 	    label/disk106  ONLINE       0     0     0
>>> 	    label/disk107  ONLINE       0     0     0
>>> 	    label/disk108  ONLINE       0     0     0
>>> 	    label/disk109  ONLINE       0     0     0
>>> 	    label/disk110  ONLINE       0     0     0
>>> 	    label/disk111  ONLINE       0     0     0
>>>
>>> which will get another enclosure with 6 750-GB-disks, soon.
>>>       
>
>   
>> I've always been curious about this. is said not good to have many disks
>> in one pool. ok then. but this layout you're using in here will have the
>> same effect as the twelve disks in only one pool ? (the space here is the
>> sum of both pools ?)
>>     
>
> It is not good to have too many disks in one group. What you see
> above is one pool with two raidz2 groups.
>
> As far as I understood the documentation after that helpful
> comment on this list, this is the recommended configuration.
>
> -------------------------------
> http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
>
> "The recommended number of disks per group is between 3 and 9.
>  If you have more disks, use multiple groups."
> -------------------------------
>
> The result is, of course, one big pool with lots of storage
> space, but the overhead necessary for redundancy is roughly
> twice that of my "dangerous" twelve-disk configuration.
>
> So I lost the equivalent of two disks or about 1 TB here.
> Fast, reliable, cheap - pick any two ;-)
>
> Kind regards,
> Patrick
>   

I see a lot of people advicing to use ZFS RAID instead of HW RAID.
I'm going to use HP duplicated iSCSI subsystems, which have autonomous 
RAID, so I'm confused about this advice.
Following the ZFS RAID stream, should I keep each disk alone in iSCSI 
and let the ZFS make the RAID job?
Should not HW RAID to be (a lot) more efficient?
Which would be the wrong side of using HW RAID with ZFS?

Thanks,

Tonino




-- 
------------------------------------------------------------
        Inter at zioni            Interazioni di Antonio Nati 
   http://www.interazioni.it      tonix at interazioni.it           
------------------------------------------------------------