11-12-2008
There's not a huge difference really. What software are you using to perform this mirroring?
To make use of either RAID0+1 or 1+0 you'll need at least 4 disks, do you have that many?
Basically RAID0+1 means that you concatenate two disks first (i.e. RAID0), and then you mirror the two RAID0 volumes (i.e. RAID1).
RAID1+0 is the reverse, i.e. you mirror two pairs of disks, and then you concatenate the two resulting volumes.
The RAID1+0 has some advantages in that if you lose one disk, you only invalidate half of one of the mirrors, so less time is required to resynchronise the data when the disk is replaced. It also means that you can lose one disk on one side, and another disk on the other side without any loss of service.
With RAID0+1, if you lose either disk in one of the concatenated volumes, you lose that whole side until the disk is replaced... which means that if you lose either of the two disks on the other side you have lost your entire volume. Multiple disk failures aren't very common, but they can happen.
So RAID1+0 has slightly better redundancy than RAID0+1. The performance and space efficiency of both is identical.
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vxpfto(1M) vxpfto(1M)
NAME
vxpfto - set Powerfail Timeout (pfto)
SYNOPSIS
vxpfto -g diskgroup -t timeout
vxpfto [-g diskgroup] -t timeout volume_list
vxpfto [-g diskgroup] -o pftostate={enabled|disabled}
vxpfto [-g diskgroup] -o pftostate={enabled|disabled} volume_list
DESCRIPTION
Powerfail Timeout is an attribute of a SCSI disk connected to an HP-UX host (see the pfto(7) man page). The vxpfto command sets the Power-
fail Timeout interval on a set of Volume Manager disks, either all disks in a disk group, or all disks underlying the volumes listed.
The first form of the command sets the same PFTO value for all the disks in the specified VxVM diskgroup.
In the second form, all disks underlying the given list of volumes are selected, optionally restricted by the disk group specified with the
-g option. If you specify a diskgroup, any volume in the list not belonging to the diskgroup is ignored.
Use the -o pftostate option to disable or enable PFTO. By default, PFTO is enabled. You can enable PFTO either on all disks in a disk
group, or on all disks underlying the volumes listed.
If you invoke vxpfto without arguments, it displays a usage message.
OPTIONS
-g diskgroup
Specifies the disk group for the operation, either by disk group ID or by disk group name.
-o pftostate={enabled|disabled}
Enables or disables the use of PFTO for IO.
-t timeout
Specifies the PFTO value in seconds. The value must be zero or a positive integer. Zero represents the system default PFTO
value. The default value depends on the disk driver controlling the disk device.
volume_list
A list of VxVM volume names. List items must be separated by white-space.
EXIT CODES
vxpfto returns a zero if successful. If it encounters an error, vxpfto exits and displays a message on standard error. Defined exit codes
are:
0 Success.
1 No PFTO value specified.
2 No diskgroup or volume list specified.
3 Illegal PFTO value specified.
EXAMPLES
Set the PFTO value on all disks in disk group testdg to 100 seconds:
vxpfto -t 100 -g testdg
Set the PFTO value to 50 seconds on all disks underlying volume01 and volume02 in disk group testdg:
vxpfto -t 50 -g testdg volume01 volume02
Set the PFTO value to 300 seconds on all disks underlying volume01 and volume02, even though they are not in the same disk group:
vxpfto -t 300 volume01 volume02
Disable PFTO on all disks in disk group testdg:
vxpfto -g testdg -o pftostate=disabled
Enable PFTO on all disks underlying volume01 and volume02i in disk group testdg:
vxpfto -g testdg -o pftostate=enabled volume01 volume02
SEE ALSO
vxdisk(1M), pfto(7)
VxVM 5.0.31.1 24 Mar 2008 vxpfto(1M)