LVM vs Internal RAID - rx2660

[Joao Rei]

What are the advantages and disadvantages using LVM or internal RAID on an rx2660?

Where is the best documentation source for configuring internal RAID?

Thanks in advance.

[Mark Nieuwboer]

hi,

with lvm you can mirror logical volumes if you want, the disadvantage is when you have to replace the disk you have to unmirror all the logical volumes and mirror it back when you repalced the disk. futher more every new logical volume you make you have to realise if you want to mirror that logical volume our not.
With raid configuration everyting is mirrorded at the 2 disks instantly. When the disk where little LVM was the better choice but nowdays the disk are big enough to do a raid configuration.

grtz. mark

[Torsten. · Accepted solution]

No need to un-mirror LVOLs in LVM if you replace a disk. You have to use pvchange -a n dev_file

But, if you mirror with LVM and you need to replace a disk - manual interaction is needed (no problem so far). The PRO is, you can use different pathes, different controllers and different disk locations to mirror your disks.

With a hardware raid controller the SPOF is the controller, but no manual action (except replacing the disk) is needed.

How to?

see

http://docs.hp.com/en/J6369-90045/index.html

HP 8 Internal Port SAS Controller Users Guide, June 2007

[Joao Rei]

And about possible issues / disavantages:

1) Disk failure alarm
2) Boot without quorum
3) How disks synch? Who is the primary disk in a HW RAID 1 config?
4) System cloning
5) Is it necessary any kind of additional LVM configuration/procedures

Any comments are apreciated.
Thanks

Joao Rei

[Torsten.]

1) Disk failure alarm
done by the diagnostics/EMS
2) Boot without quorum
"boot vmunix -lq" for LVM
3) How disks synch? Who is the primary disk in a HW RAID 1 config?
automatic sync. if you replace a disk in LVM you have to configure it. There is no "primary" in both cases, but "Participating Physical disks"
4) System cloning
ignite is recommended for cloning hp-ux systems (both cases)
5) Is it necessary any kind of additional LVM configuration/procedures
To do what???

[Steven E. Protter]

Shalom,

1) Disk failure alarm
That is a problem either way, the system keeps running and in LVM you need as script to check dmesg. In hardware raid a light comes on on the front of the server.

2) Boot without quorum
No problem with hardware raid.

3) How disks synch? Who is the primary disk in a HW RAID 1 config?
2 disks in HW RAID 1.

4) System cloning
No impact.
5) Is it necessary any kind of additional LVM configuration/procedures
None.

Hardware Raid has an advantage over LVM. None of the work uses system memory or CPU resouces. The Hardware RAID card has its own CPU and RAM to maintain the raid set. This normally provides better performance than mirror/ux

SEP

[Torsten.]

I would configure the internal RAID. This makes life easier.

Most problems are created by users doing the wrong steps during a disk replacement. You cannot count related threads here in this forum ...
I guess many people are just doing without reading before ...

[Geoff Wild]

I just finished setting up hardware mirroring on a RX6600 - very slick and fairly easy to do.

I used the same doc Torsten pointed to - basically, EFI Shell and the drvcfg utility.

Rgds...Geoff

[Joao Rei]

This thread helped me to decide create an IM volume.

I have two disks. One contains HP-UX v2.
I want to create an IM volume and keep the O.S.

When creating the IM in drvcfg Ive choosen "M" - Keep existing data

But I received this warning:

"
WARNING! There is currently not enough empty space at the end of this disk to create an array. Using this disk in an array will result in loss of ALL data on the disk. "

From the SAS User Guide:
"...
Press M to keep the existing data, synchronize the contents of the Primary and Secondary
disks, and create a logical volume with RAID 1 mirroring."

Is It possible to mirror the O.S.? From the warning It says I cant.

Has someone experienced this?
Any ideas?

Tanks in advance

Joao Rei

[Joao Rei]

The "M" option on drvcfg (Keep existing data) can only be used on disks that do not contain EFI partitions.

To keep the O.S. I'll create an IM with two other disks. Mirror with Mirrordisk/UX the O.S. and the IM. Finally, unmirror the original S.O disk and keep the IR volume.