[Cialug] What should I be asking?

[Theron Conrey]

Matt,

I'll assume that you're talking about using the Vmware ESX environment and not the free server setup and answer from there.

Some things to consider:
        What type of storage are you using? Is it NFS, iSCSI or fiber?  Given the fact they're all Windows VM's I'll assume that you're either an iSCSI or fiber shop.

If you're iSCSI there are issues related to SCSI disk timeouts and Linux VMs.  These aren't show stoppers by any means (we're an iSCSI shop) but they do present some configuration challenges.  And example would be the SCSI timeout settings.  This # is higher in windows (and easier to change) than in Linux by default, and can cause issues if you're using a journaling file system (ext2/3 as an example).  The last thing you want is a "local disk" having SCSI IO lag and causing your entire file system to go read only.  There are ways around this, (downloading an updated driver to compile into your kernel from VMware, link escapes me atm) and just requires some prior planning.

The kernel brings up another issue, in Xen (talking about the default Xen configuration in RHEL5) paravirtualization is implemented, so the danger of kernel updates isn't as prevalent, however, with a fully virtualized environment such as VMware's ESX, a kernel upgrade on a VM has the capacity to whack the network/SCSI drivers and cause the system to go offline.

(still irritating is there a safe what with YUM/puppy/whatever-redhat-is-doing-these-days to disable kernel upgrades during updates from the mothership?)

In the past I've just run my own internal repo for updates to avoid this issue.

Just a couple of one off things to think about prior to going down the road.

-Theron




-----Original Message-----
From: cialug-bounces at cialug.org [mailto:cialug-bounces at cialug.org] On Behalf Of Matt Millard
Sent: Wednesday, September 26, 2007 10:19 AM
To: Central Iowa Linux Users Group
Subject: [Cialug] What should I be asking?

I've got a meeting this afternoon to discuss adding RHEL to our fairly large VMWare environment that is currently all Windows VM's.  I've twittled the knobs on Xen running on RHEL5, but not more than doing a single install.  I'm just curious what are some things that I should be on the look out for in the VMWare environment that has been built around only installing Windows servers?  Any suggestions would be greatly appreciated.

So glad the VUG is starting up as I'll be getting in deeper sooner than later!

Matt
---
  Matt Millard
  gocyclones at eml.cc
  http://photos.millardfam.com
  http://yepr.com/MattsItems

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