[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [Linux-cluster] Storage Cluster Newbie Questions - any help with answers greatly appreciated!



Rafael,

Appreciate the link to - Brem's script.  - I had actually found that previously - and I think the piece of the puzzle I'm missing to make that useful - is figuring out how to disable either the auto-load of "qla2xxx" (my fiber card HBA) and/or disable the auto-find and reassemble on boot of all - mdadm volumes... or as Leo said - allow it all to start, but put in a S00 - mdadm stop script (which seems a bit too much like a hack for my tastes).

As for the CLVM w/mirrors... just reading through the technical docs - made me worry... your results are about on par with what I was thinking... which is I - would like to - wait a few more releases before I play with that in a Production mode.

-Michael

Rafael Micó Miranda wrote, On 3/11/2010 3:13 PM:
Hi Michael

El mié, 03-03-2010 a las 11:16 -0800, Michael @ Professional Edge LLC escribió:
Hail Linux Cluster gurus,

    

[...]

 From what I can find messing with Luci (Conga) though... is - I don't 
see any resource scripts listed for - "mdadm" (on RHEL 5.4) - so would 
my idea even work  (I have found some posts asking for a mdadm resource 
script but I've seen no response)?  I also see with RHEL 5.3 LVM has 
mirrors that can be clustered now - is this the right answer?  I've done 
a ton of reading but everything I've dug up so far; assumes that the 
fiber devices are being presented by a SAN that is doing the redundancy 
before the RHEL box sees the disk... or... there are a ton of examples 
of where fiber is not in the picture and there are a bunch of locally 
attached hosts presenting storage onto the TCP (ethernet) - but I've not 
found nearly anything on my situation...

    

You can find an unofficial MDADM rgmanager resource script at this topic:

https://www.redhat.com/archives/linux-cluster/2009-August/msg00111.html

The resource was developed by Brem Belguebli, maybe if he sees this topic he could give you more detail of the capabilities of the resource script and it's compatibility with LVM / CLVM on top of it.

In the other hand, you can use directly mirrored LVM volumes with CLVM. I made some testing with the behaviours of mirrored LVM and I found some strange stuff when only one node fails its connection to the device - in your situation it will happen when one of the nodes fails one of the links with one of the shelves. The fact was the device being marked as "unknown device" in the node with the failed path, and in the other everything seemed ok. What can happen during the "reconstruction" of the failed volume can be unpredictable. Note the "99.6" in the Copy% column, it always had the same value while the path was failed:

NODE A
lvs -a -o +vg_name,device
LV                      VG       Attr   LSize   Origin Snap%  Move Log               Copy%  Convert VG       Devices                                         
logvolquorum            volgrp01 mwi-ao 996,00M                   logvolquorum_mlog 100,00         volgrp01 logvolquorum_mimage_0(0),logvolquorum_mimage_1(0)
[logvolquorum_mimage_0] volgrp01 iwi-ao 996,00M                                                     volgrp01 /dev/mpath/quorum01(0)                          
[logvolquorum_mimage_1] volgrp01 iwi-ao 996,00M                                                     volgrp01 /dev/mpath/quorum02(0)                          
[logvolquorum_mlog]     volgrp01 lwi-ao   4,00M                                                     volgrp01 /dev/mpath/logquorum01(0)    


NODE B (failed path)
lvs -a -o +vg_name,device
LV                      VG       Attr   LSize   Origin Snap%  Move Log               Copy%  Convert VG       Devices                                         
logvolquorum            volgrp01 mwi-ao 996,00M                    logvolquorum_mlog  99,60         volgrp01 logvolquorum_mimage_0(0),logvolquorum_mimage_1(0)
[logvolquorum_mimage_0] volgrp01 Iwi-ao 996,00M                                                     volgrp01 /dev/mpath/quorum01(0)                          
[logvolquorum_mimage_1] volgrp01 Iwi-ao 996,00M                                                     volgrp01 unknown device(0)                               
[logvolquorum_mlog]     volgrp01 lwi-ao   4,00M                                                     volgrp01 /dev/mpath/logquorum01(0)  


I hope this brings some light to your questions.

Cheers,

Rafael

-- 
Rafael Micó Miranda
        



[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]