topic Re: Mount same harddisk by 2 hostname in Operating System - HP-UX

Mount same harddisk by 2 hostname

aaronleung_1 — Sat, 30 Dec 2000 03:28:43 GMT

Hello All

I want to know is it possible to mount a hardisk(PV) by more than one hostname at the same time. Is it possible to mount this pv by both host using read/write mode.

Regards,

Aaron

Re: Mount same harddisk by 2 hostname

James R. Ferguson — Sat, 30 Dec 2000 05:05:38 GMT

Hi:

In the absence of high-availability software like MC/ServiceGuard, the simultaneous activation of a volume group for read/write access by more than one server invites data corruption. A good overview of access concurrency can be found in the man pages for 'vgchange'.

...JRF...

Re: Mount same harddisk by 2 hostname

Ajitkumar Rane — Sat, 30 Dec 2000 15:21:43 GMT

No. To my knowledge as of now hpux does not support read/write on a PV at the same time by 2 hosts.Even with MC/SG, its when one host fails and releases the PV the other activates it and mounts it,so its one host accessing at a time.

Re: Mount same harddisk by 2 hostname

CHRIS_ANORUO — Sat, 30 Dec 2000 15:54:19 GMT

Hi aaronleung,

It is not done as has been pointed out by the previous contributions.
Check these documentations:
http://docs.hp.com/hpux/ha/index.html#ServiceGuard

Re: Mount same harddisk by 2 hostname

Ovidiu D. Raita — Sun, 31 Dec 2000 02:24:03 GMT

Theoretically you can mount the same file system/LV (not PV) on two different systems at the same time.

If you mount them read/write on both you'll face data corruption (HFS nor vxfs are designed to handle multiple rw accesses). Just imagine that the two systems will try to update the inode tables with two different versions at virtually at the same time and you can be 100% that the inode table will get corrupted.

These being said you can mount the fs/LV read/write on one and just read on another. The solution to your problem seems to be NFS that is by definition a Network File System and has built in mechanisms to handle the situation.

Good luck,
Ovidiu

Re: Mount same harddisk by 2 hostname

aaronleung_1 — Tue, 02 Jan 2001 01:28:33 GMT

Hello,

Is it possible to mount the same pv by 2 host, one is mount with rw mode, but the others is mount with read only mode. I don't want to use nfs, is it any other way to do it.

Aaron

Re: Mount same harddisk by 2 hostname

John Waller — Tue, 02 Jan 2001 12:57:14 GMT

Hi,
You keep mentioning a pv (physical volume). Are you wanting to mount a single disk as a raw device on 2 systems or do you want to mount a logical volume on 2 systems? If we are talking about logical volumes and volume groups then you need to make sure that the disk is not part of vg00 (root). If it is NOT you could can create and activate the volume group on 2 systems and as long as you make sure that you mount the logical volume (filesystem) as read only on one you should be OK. This is not possible for vg00. If you are wanting to use a disk device as a raw disk on two systems again I believe you should be able to mount the disk as read only on one of the systems similar to mounting a CD-ROM. One thing you need to be careful of is making sure you have correct SCSI termination and different SCSI ID's on the SCSI controllers, or else you could have serious hardware problems by having a disk shared by 2 systems

Re: Mount same harddisk by 2 hostname

Ovidiu D. Raita — Tue, 02 Jan 2001 13:47:39 GMT

No other choice. You have to use NFS.
Ovidiu

Re: Mount same harddisk by 2 hostname

Emil Velez — Tue, 02 Jan 2001 20:36:14 GMT

You cannot mount a LV on 1 system with read/write and the other with read

The read write system will change the metadata and the read only system will have metatadata that is now incorrect in memory. Why not use NFS ? The TCP version is available with 11i.