Mirror-UX needed with Raid?

[Tim Medford]

We are planning to buy a couple rx class Itanium boxes later this year. I haven't worked with them, but it's my understanding that they support Raid controllers and provide hardware mirroring.

If I have vg00 consist of 3 physical disks setup in a Raid5 LUN, would I really need to run mirror-ux on top of that? I'm not even sure how I would set that up, because the OS would see that Raid configuration as 1 large drive.

I understand that with this setup I could lose 1 drive and still be ok. Hoprfully the new drive is replaced before another one dies.

Am I missing something here or has anyone else tried this?

Thanks, Tim

[Ivan Ferreira · Accepted solution]

>>> If I have vg00 consist of 3 physical disks setup in a Raid5 LUN, would I really need to run mirror-ux on top of that? I'm not even sure how I would set that up, because the OS would see that Raid configuration as 1 large drive.

No. Mirror UX is needed for setting RAID by sofware. You already have RAID by hardware so you don't need it.

[Pete Randall]

Generally hardware RAID is external to the box and, if you are going to use the internal drives for VG00, you will need MirrorDisk to provide the necessary redundancy. It is possible to have VG00 on external (RAID) storage, but I would recommend RAID 1/0 before RAID 5.


Pete

[Peter Godron]

Tim,
I don't think MirrorUX can be set up to Raid 5 anyway. Reading your description, your setup should work.

[DCE]

Tim,

If you are doing hardware mirroring, there is no need to use the software mirroring product. It would just add overhead, and not really add any redundancy to the system.

Are the disks in the unit you are looking at hot swappable with out removing the case cover? (I assume you are talking about using raid 5 on the internal disks)

[A. Clay Stephenson]

"Normally" when using dedicated arrays, Mirror/UX is not used but it is used to mirror data across separate arrays. I'm a bit old-fashioned but I tend to avoid arrays for vg00 -- if the machine won't boot, I want as little as possible between the boot drive and the host computer so that troubleshooting is easier. The other "gotcha" is making sure that you have multiple paths to your data. While RAID5 handles the loss of a disk, it says nothing about the failure of a cable or disk controller (althogh that may be covered as well by your particular hardware).

[Steven E. Protter]

Shalom Tim,

Running mirror/ux to mirror on top of raid 5 would be a very, very bad idea that could inroduce all kinds of performance problems.

Hardware raid as noted is better because it takes work from the cpu and leaves it free for other things.

I like to do raid 1 mirroring on the boot disk so the system continues to function if it loses one of its disk.

That does require mirror/ux

Its better to have raid 1 in place from the beginning of system life to avoid sudden problems.

SEP

[Tim Medford]

Thanks for the input everyone.

Pete - Yes, I agree normally the RAID is on a separate disk array. This has always been the case for us anyway, and then I would mirror the root drives with Mirror-UX.

What is different in this case, and I've only heard rumors to this point, is that the newer boxes are coming out with builtin Raid right in the chassis. So assuming those SATA or SAS drives are hot-swappable it would obviate the need for software mirroring.

We've handled windows proliant servers this ways for a long time. I personally would welcome this kind of support for hpux rather than bothering with mirrorUX.

I'll send out another post when I get things configured and let everyone know how it worked out.

[Steven E. Protter]

Some newer HP-UX systems are shipping with RAID cards.

This negates the need to use mirror/ux.

Here is a procedure to do the software mirror.

It needs to be modified to work on 11.23, but works well on 11.11 PA-RIsC.

pvcreate -B /dev/rdsk/c1t0d0 #use real disk

mkboot -l /dev/rdsk/c1t0d0
mkboot -a "hpux -lq (;0)/stand/vmunix" /dev/rdsk/c1t0d0 # use real disk


# mkboot -b /usr/sbin/diag/lif/updatediaglif -p ISL -p AUTO -p HPUX -p PAD -p LABEL /dev/rdsk/c?t?d?

If you are running 64-bit OS:

# mkboot -b /usr/sbin/diag/lif/updatediaglif2 -p ISL -p AUTO -p HPUX -p PAD -p LABEL /dev/rdsk/c?t?d?


vgextend /dev/vg00 /dev/dsk/c1t0d0 # same thing
lvextend -m 1 /dev/vg00/lvol1 /dev/dsk/c1t0d0

# real disk. repeat for other lvols

lvlnboot -r /dev/vg00/lvol3 # root fs /
lvlnboot -s /dev/vg00/lvol2 #swap
lvlnboot -d /dev/vg00/lvol2 #swap/dump
lvlnboot -b /dev/vg00/lvol1
lvlnboot -R
lvlnboot -v
setboot
setboot -a 52.1.0 # second disk

Cheers,

Happy Admining.

SEP