Raid 1+0

[Michael Powell]

Bernt Hansson wrote:

> Hello list
> 
> My motherboard has a raid chip on it (AMD SB750), so my plan was to use
> it. Since i never used the chip for raid, i thought i might try.
> 
> So far this has been done.
> 
> Set up 2 arrays with 2 discs in each array with raid1 on both.
> 
> Boot up freebsd 10.3-R. Both arrays are found
> 
> GEOM_RAID: Promise: Disk ada0 state changed from NONE to ACTIVE.
> GEOM_RAID: Promise: Subdisk RAID 1   LD  1:0-ada0 state changed from
> NONE to ACTIVE.
> GEOM_RAID: Promise: Disk ada1 state changed from NONE to ACTIVE.
> GEOM_RAID: Promise: Subdisk RAID 1   LD  1:1-ada1 state changed from
> NONE to ACTIVE.
> GEOM_RAID: Promise: Volume started.
> GEOM_RAID: Promise: Volume RAID 1   LD  1 state changed from STARTING to
> OPTIMAL.
> GEOM_RAID: Promise: Provider raid/r0 for volume RAID 1   LD  1 created.
> GEOM_RAID: Promise: Disk ada2 state changed from NONE to ACTIVE.
> GEOM_RAID: Promise: Subdisk RAID 1   LD  2:0-ada2 state changed from
> NONE to ACTIVE.
> GEOM_RAID: Promise: Disk ada3 state changed from NONE to ACTIVE.
> GEOM_RAID: Promise: Subdisk RAID 1   LD  2:1-ada3 state changed from
> NONE to ACTIVE.
> GEOM_RAID: Promise: Volume started.
> GEOM_RAID: Promise: Volume RAID 1   LD  2 state changed from STARTING to
> OPTIMAL.
> GEOM_RAID: Promise: Provider raid/r1 for volume RAID 1   LD  2 created.
> 
> Used gstripe to stripe the arrays raid/r0 + r1 into stripe0
> 
> Newfs/mount all work. My question, is this a raid 1+0 or 0+1?

This is RAID 1+0. Characteristics of such gives better I/O performance for 
lots of small random reads/writes such as the way a database server uses 
disk. 

The flip side of this (RAID 0+1) will have better performance for sequential 
throughput for use such as file server for storing backups and other large 
files.

-Mike