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Raid 1 Boot Disk |
taunusstein-net
Member
Posts: 17
Joined: 16.10.09 |
| Posted on December 20 2010 09:00 |
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Hello,
it seems license VOLSHAD is the right one, it provides Raid1. Does anybody have experience how to become system disk a Raid1 device ?
I would like to get
* dka0
* dka100
mirrored. OpenVMS is installed at dka0. SRM should boot from dka0 or dka100 but OpenVMS should always use "shadow" device DSA0 (ist that the right one ?)
best regards
Christian |
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RE: Raid 1 Boot Disk |
martinv2
Member
Posts: 107
Location: Goslar, Germany
Joined: 02.10.07 |
| Posted on December 20 2010 16:07 |
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Christian,
volume shadowing is so important for VMS that it has a manual of its own:
http://h71000.www7.hp.com/doc/732final/aa-pvxmj-te/aa-pvxmj-te.html
The chapter on "Preparing to Use Volume Shadowing" details all steps you need to complete. The extra steps required to shadow a system disk are covered, too.
- Install VOLSHAD license
- Set volume shadowing system parameters
- Shutdown
- Set SRM variable bootdef_dev to a blank-separated list of all members of the shadow set
- Boot from first member
- Add second member to the shadow set
HTH
Martin
http://de.openvms.org/martinv/ |
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| Author |
RE: Raid 1 Boot Disk |
taunusstein-net
Member
Posts: 17
Joined: 16.10.09 |
| Posted on December 20 2010 21:50 |
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Martin,
thank you very much, now I got my OpenVMS boot disk mirrored :-)
Christian
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RE: Raid 1 Boot Disk |
urbancamo
Member
Posts: 47
Location: Windermere, UK
Joined: 16.05.07 |
| Posted on December 25 2010 21:01 |
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I blogged about this a while back (as much to remind myself in future than anything else):
http://lakesdev.blogspot.com/2009/09/volume-shadowing-system-disk-on-vax.html
Might help some one out... |
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RE: Raid 1 Boot Disk |
martinv2
Member
Posts: 107
Location: Goslar, Germany
Joined: 02.10.07 |
| Posted on December 26 2010 16:29 |
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Mark,
thanks for the link; a nice roundup. Some annotations, though:
- There also is a license named VOLSHAD-DISK. The units on that one determine how many shadow sets can be active.
- I'd recommend against using an ALLOCLASS value of 1 or 2, if you ever want to use Fibre Channel. FC disks and tapes, respectively, come with these hard-coded values for their allocation class.
- There is another interesting system parameter to be set: SHADOW_MBR_TMO (and SHADOW_SYS_TMO for system disks). A value of 8 (seconds) was used in the Disaster Proof Experiment, as described here. This setting, among others, enabled VMS to win the race to recover in 13.71 seconds.
cu,
Martin
http://de.openvms.org/martinv/ |
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RE: Raid 1 Boot Disk |
somersdave
Member
Posts: 67
Location: bristol,UK
Joined: 23.03.07 |
| Posted on January 01 2011 07:24 |
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From my amateur hobbyist perspective, it appears that RAID can be implemented in two different ways.
It seems can either be implemented from within OVMS (as above) or pre boot. I can't remember my reasoning at the time but as my Alpha 4000 had a SWXCR RAID controller I discovered that I needed to 'invoke' Alphabios rather than SRM in order to configure RAID 5 (i can't remember why 5, either - much of my hobbying seems to be on hunches ).
I haven't got the machine powered up at the moment but i don't recall any license warning messages pre license installation and so I was under the impression that RAID (as I have it) was something outside/below OVMS.
I've seen some comments about whether the CPU or controller handles the shadowing overhead.
When the alpha 4000 boots, it reports '5 MEMBER RAID 5 , 0 failed, 1 degraded' (or something like that).
One of the 9 Gig disk 'bricks' had failed and so I replaced it but the 'degraded' message still remains. I assumed that the message would eventually disappear after the configuration healed itself - perhaps I need to do some RAID installation from within OVMS?
Edited by somersdave on January 01 2011 08:27 |
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RE: Raid 1 Boot Disk |
martinv2
Member
Posts: 107
Location: Goslar, Germany
Joined: 02.10.07 |
| Posted on January 02 2011 05:25 |
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From my amateur hobbyist perspective, it appears that RAID can be implemented in two different ways.
There are at least four ways:
- Controller-based RAID - That's what you have with your SWXCR. VMS doesn't even know the disks it uses are RAIDsets.
- (Host-Based) Volume Shadowing - Also called mirroring. What the above discussion is about.
- Bound Volumesets - This is also called striping, or RAID 0.
- There also is a RAID software for VMS that implements RAID 5.
When the alpha 4000 boots, it reports '5 MEMBER RAID 5 , 0 failed, 1 degraded' (or something like that).
One of the 9 Gig disk 'bricks' had failed and so I replaced it but the 'degraded' message still remains. I assumed that the message would eventually disappear after the configuration healed itself - perhaps I need to do some RAID installation from within OVMS?
IIRC, you have to manually put the replacement drive back into the RAIDset. As this is below VMS, you have to do it via the controller setup. But don't quote me on that one.
cu,
Martin
http://de.openvms.org/martinv/ |
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RE: Raid 1 Boot Disk |
abrsvc
Member
Posts: 108
Joined: 12.03.10 |
| Posted on January 06 2011 04:19 |
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Minor correction: Voluime sets are NOT striped. Striping implies that there are pieces of each file on each member. While this is possible with volume sets, it is not the norm. Volume sets allow for larger overall space within the context of a singe drive. The files are allocated on the basis of free space on each component drive. In other words, when a file is created, it will reside on the drive that had the most free space at the time of creation. Until "recent" versions of VMS, there was a limit to the file size of the capacity of the single drive it landed on. This was changed so that you can now have files that span physical drives.
Dan |
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