I was wandering for a long while about the connection between NetApp’s LUN Serial and the identifier the host sees, aka “Word 83″. There was an obvious connection, but I figured it out only today.
The LUN Serial is an ASCII representation of the hexadecimal Word 83, or, to be exact, the last 22 hex characters of it.
lun serial /vol/volume/qtree/lun
When querying the multipath device represented there, we get:
Following some unknown problems, I had recently several XenServer machines (different clusters, different sites and customers, and even different versions) with a VDI-END-of-File issues. It means that while you can start the VM correctly, perform XenMotion to another server you are unable to do any storage-migration task – neither Storage XenMotion, nor VDI copy or VM-move commands. In some cases, snapshots taken from the “ill” disks were misbehaving just the same. This is rather frustrating, because the way to solve it is by cloning the disk into a new one, and your hands are bound.
This is a very nice project I have been working on. The hardware at hand – two servers, with a shared SAS bus containing several SAS disks. Since it’s a shared bus, no RAID solution would cut it, and as I don’t want to waste disks with ASM (“normal” redundancy meaning half the size…), I went to ZFS storage.
ZFS is a wonderful technology, with many advantages, but with some dangerous pitfalls. As I prefer Linux, I did not bother with any Sloaris solutions, and went directly to Centos 6. I will describe my cluster setup below.
Well, tricks is not the right word to describe advanced shell scripting usage, however, it does make some sense. These two topics are relevant to Bash version 4.0 and above, which is common for all modern-enough Linux distributions. Yours probably.
These ‘tricks’ are for advanced Bash scripting, and will assume you know how to handle the other advanced Bash topics. I will not instruct the basics here.
Trick #1 – redirected variable
What it means is the following.
This post will describe the process of placing SSH keys using the internal ‘systemshell’ command of NetApp. As always – when doing something which the vendor did not intend you to do, do it very carefully. This data was obtained from NetApp forums, and while I do not have the original post to link (I usually link to the original, as a courtesy to the original author), this is the content, as is.
First, set to advanced mode:
filer> priv set advanced
I migrated to dnsmasq just yesterday, and discovered that a Windows 7 machine was hammering the server with messages like this:
Feb 1 11:06:07 dns dnsmasq-dhcp: DHCPINFORM(eth0) 192.168.1.77 91:de:87:7b:e5:a8
Feb 1 11:06:07 dns dnsmasq-dhcp: DHCPACK(eth0) 192.168.1.77 91:de:87:7b:e5:a8 winpc
I love XenServer. I love the product, I believe it to be a very good answer for SMBs, and enterprises. It lacks on external support, true, but the price tag for many of the ‘external capabilities’ on VMware, for instance, are very high, so many SMBs, especially, learn to live without them. XenServer gives a nice pack of features, at a very reasonable price.
A quick note about extracting and recreating RHEL6 or Centos6 (and their derivations) installation media components:
mv initrd.img /tmp/initrd.img.xz
xz –format=lzma initrd.img.xz –decompress
cpio -ivdum < ../initrd.img
The goal – connecting multiple Oracle ASM snapshots (same source LUNs, of course) to the same machine. The next process will demonstrate how to do it.
The following procedure was tested by me, and was found to be working. The version of the XenServer I am using in this particular case is 6.1, however, I belive that this method is generic enough so that it could work for every version of XS, assuming you're using iSCSI and LVM (aka - not NetApp, CSLG, NFS and the likes). It might act as a general guideline for fiber channel communication, but this was not tested by me, and thus - I have no idea how it will work.