RAID & Mirroring?

[Jenifer Martins]

I am suppose to find out if this can RAID or Mirroring can be done on HP-UX 10.20. Obviously, I do not know a thing about this and where to start. Can anyone tell me if this can be done and what is involved... hardware, software? I would like to understand this option.... currently, the OS is on the internal drives (5) 4GB drives. The data is on two storage units with (4) 18.2 GB drives in each. Currently, the data is at about 25% usage of each storage unit. Please help!

[Michael Tully]

Hi Jenifer,

You can you both disk mirroring and RAID on
HP-UX 10.20. RAID can only be used on certain
types of equipment, i.e. an autoraid or a
storage area network, like an XP256, 512 or
EMC. Can you identify what type of disk units are
being used? Perhaps you can supply an output of
'ioscan -fn' to the forum.

One of the easiest ways to find if you are using
disk mirroring and that is to issue

# lvdisplay -v /dev/vg00/lvol1 | grep -i mirror
This will show whether you have one of your
vg00 (root volume group) logical volumes
mirrored and
# swlist -a revision | grep -i b2491
this will determine if the mirroring software has
been installed.


here's starting point. HTH
Michael
HTH
Michael

[James R. Ferguson]

Hi Jenifer:

There are (at least) two important things to remember when discussing mirroring on HP-UX.

1. Most generally, mirroring is implemented at the OS level with the MirrorDisk/UX product. This is an optional product which you license and install from the Application CDROM set.

2. MirrorDisk/UX leverages LVM functionality and mirrors logical volumes *not* disks. That is, for each logical volume within a volume group it is necessary to explicitly mirror logical volumes. A very good overview of mirroring can be found in the "HP-UX System Administration Tasks" manual:

http://docs.hp.com/hpux/onlinedocs/B2355-90672/B2355-90672.html

...JRF...

[John Waller]

Jenifer,

You need to be careful when talking about RAID and mirroring. To some users a RAID device is a stand alone set of disks which has its own controller. These are normally setup via their own software and when used under HP-UX or any other O/S are treated as a single disk device.
What you have expained is a standard disk storage device which has two disk. The O/S will see these disks as seperate devices and you will need to rely on the O/S to setup the disk.
If somebody mentions RAID 1 then they are talking about disk mirroring, (lvextend -m 1 /dev/vgxx/lvol??), but this requires the purchase of MIRRORDISK/UX. (use swlist to confirm if this has been loaded). Other RAID levels like RAID 3 and RAID 5 cannot really be performed with your setup.
This is prabably as clear as mud but I hope it helps.

[Bill McNAMARA_1]

Hi,

Mirroring your data is creating a RAID 1 structure.
This can be done with MirrorDisk/UX on any lvm capable disk including the boot disk.... and is recommended for the bootdisk.
When a disk fails you can boot off the mirror and don't have to reinstall, restore from backup. That's the advantage.

Disadvantage is that s/w raid either by LVM or VxVM is slow.. in comparisson to dedicated raid h/w.
Dedicated Raid H/W is the likes of the AutoRAID, does not require s/w to do the RAID, it's handled by the controllers.

See the Storage Forum for more.

Later,
Bill

[Mike Shilladay]

Hi Jenifer,

The simple answer to your question is yes HP-UX 10.20 can use RAID and/or Mirroring, what you wish to achieve i another kettle of fish.

Assuming that you do not want to spend any money then the first thing to do is to check for the optional product MirrorDisk/UX (B2491BA). If you have this then you can either make 1 or 2 mirrors of the logical volumes. You can also make a duplicate of the root disk, this requires a little more knowledge as this is not quite as straight forward as extending the logical volume with the lvextend -m 1 /dev/vg??/lvol?? /dev/dsk/ command.

You can also "fudge" a RAID type environment using HP-UX commands, but this still impacts on the CPU as it is using LVM. You can either obtain a sumulated RAID 0 (striped), RAID 0+1 (striped and mirrored) or RAID 1 (mirrored).

If you wish to get more grunt out of the Disk I/O, then a dedicated RAID device is required, an example being the Model 12H AutoRAID (A3700A) although this requires at least 1 FWD interface. Less expensive RAID solutions can be obtained from 3rd parties but ensure that the drivers are supplied and that it is supported in your environment. Further upmarket there are devices such as the FC60 based on fibre. The XP48, 256 or 512 will give shed loads of room, but it sounds as though that is going too far.

It should be noted that there is usually extra S/W to provide a user interface to the RAID array if it is hardware based. (i.e. not using LVM).

I do not believe that the Model 12H AutoRAID allows boot functionality, this has to be provided by MirrorDisk/UX. It is probably best to observe that Hardware RAID solutions will not be a supported Boot Device.

Hope this helps.

Mike.