How to do the s/w mirror in J5600

[Manikandan k]

Hi,
We are planning to get a new HP-UX workstation model J5600. Our customer requirement is 36GB has to be mirrered for storing a main data.
So i decided 18GB for OS, 2x36 GB for main data. This server supports max. of 4 drives. Our requirement is HP-UX 11.0. Can anyone provide me a guide line for s/w mirroring of 2x36 GB.

Thanks and Best regards
Mani

P.S. This thread has been moved from  Disk to HP-UX > sysadmin. -HP Forum Moderator

[Stefan Saliba · Accepted solution]

To mirror two disks you first need a license for a software called MirrorDisk/UX. Once you install this software you can mirror your logical volumes using the lvextend command. Checkout the man page for a full explanation of the switches in lvextend.

But usually you would do somthing like

lvextend -m 1 /dev/vg00/lvol1 to create a single mirror of lvol1.

of course the volume group containing the VG should at least have to disks.

Good luck
Stefan

[Manikandan k]

Hi Stefan,
Thanks a lot for your information.

For MirrorDisk/UX require 3 identical disks or 2 disks?. In my case, J5600 workstation supports maximum of 4 internal disks, ie.,
-----------------------------------------
Ultra2 SCSI LVD 80 pin SCA connector
4 drives maximum
hot pluggable (requires HP mirrordisk/ux)
18GB (10K RPM)
36GB (10K RPM)
36GB (15K RPM)
73GB (10K RPM)
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This above informaton has copy pasted from the J5600 worstation spec.

And below is the MirrorDisk/UX Software detail taken from hp site.
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MirrorDisk/UX License for Servers
Introduction

MirrorDisk/UX software prevents data loss due to disk failures by maintaining up to three copies of data on separate disks. Applications can continue to access data even after a single disk failure. In addition, you can perform on-line backups to avoid user and application disruption.

To prevent the failure of a single I/O interface from causing a system failure, HP recommends that mirrored disks be connected to separate interface cards.

Features and Benefits

No single point of failure - separate controllers/power supplies
Up to 3-way disk mirroring
On-line backup while maintaining mirroring
Application transparency
Dynamic mirror configuration
Selective mirror of data
Fast data synchronization
Menu-driven administration tools
Because high availability solutions require full-time access to data, HP has developed MirrorDisk/UX to provide mirroring capability within the HP-UNIX?? Operating System (HP-UX) environment.

MirrorDisk/UX, the mirroring component of Logical Volume Manager (LVM) from the Open Software Foundation (OSF???), prevents data loss by maintaining up to three copies of data on separate disks. This enables data to remain intact after a single disk or interface card failure.

MirrorDisk/UX can mirror a disk partition, including the root and swap partitions. It supports mirroring of raw disk access as well as file system access. MirrorDisk/UX can increase input/output (I/O) disk performance depending upon the mix of disk reads and writes.

Because MirrorDisk/UX works with the HP-UX kernel to manage the mirrored disks, it is transparent to the applications, which require no modification.

MirrorDisk/UX allows customers to perform a backup by taking one disk of a mirrored pair offline while the other disk continues to service applications. As the backup is being performed, the changes occurring to the online disk are maintained in table memory. Upon completion of the backup procedure, a faxt update is done to synchronize the disks while application continuity is maintained. To prevent the possibility of data loss caused by a failure during a backup, three-way mirroring provides a fully redundant mirrored pair while the third copy is being backed up.
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My question is
If Mirror Disk/UX requires 3 disks
1. This server supports 4 drives, so i can go for 1 disk for OS and 3 Disks for Mirroring.
or
If Mirror Disk/UX requires 2 disks
1 disk for os and 2 disks for Mirroring on this server.

Thanks and Regards
Mani

[Stefan Saliba]

MirrorDisk/UX requires 2 or 3 disks depending if you are doing 1 or 2 way mirroring.

Let me explain,

You can use mirrordisk UX to have a HD and mirror it on another HD. This is one way mirroring and requires 2 HDs. (1 data 1 mirror)

You can be extra safe and say, I have a HD and I want two copies of the mirror. This is 2 way mirroring, and so you require 3 disks in all (1 data 2 mirror)

The advantage of 2 way mirroring is you can split the mirror to take backups and still have one mirror available. If you do that with one way mirroing then when you split to take backups you are left without mirror.

My suggestion is this.
You can have a total of 4 disks, so what I would do is one way mirror OS disk (requires 2 HD) and one way mirror data disk (requires 2 HD).

Total of 4hd's then will be needed and you will be safe all the way.

I strongly suggest you mirror OS disk as well.

Good Luck

Stefan

[Stefan Saliba]

What I also strongly suggest it to go to HTTP://docs.hp.com and get a book called "HP-UX System Administration Taks". In this book there is an in-depth explanation of mirroring and the actual commands to make your mirroring work.

It is good to read before you actually perform the mirroring tasks. It will help clear any misconceptions

Good Luck

Stefan

[John Downs_1]

Another difference between 2 and 3 disk
mirrors is: With the two disk option your data will go offline when you loss one of the disks. If you loss one disk in the three disk setup your data stays online.

-john