Case of the high disk activity

A Blog by Ben Lavender

So it’s finally Friday here and I was driving to the office this morning when I thought about another idea for a tech-blog that I could share with our customers.

Now whenever I get stuck for ideas on where to begin with a technical issue I always remember Mark Russinovich quoting David Solomon in one of his Sysinternals TECHED sessions with “When in doubt, run Process Monitor!” By the way, I suggest watching some of them as you’ll learn a whole lot about Wininternals, I’ll link in some stuff from him at the end of this blog.

So what was the issue? I was asked by my MD to look at an issue with an Apache server running Windows Server 2008 R2, this was running Apache 2.2.22 and a certain process was hitting the disk quite heavily and also slowing the site rendering speed. We knew of the high disk write counts after a quick look using perfmon.exe.

As a starting tool on Windows I also use Performance Monitor (perfmon.exe) and Resource Monitor (perfmon.exe /res) and I particularly enjoy the Data Collector Sets (DCS) that you can use as filters, but I’m more of a Sysinternals guy when it comes to analysis.

*You can use the below perfmon.exe DCSs if you want to look deeper into Disk I/Os:

1

 

*Also generally looking at perfmon.exe /res “Resource Monitor” live screens will give a good idea of the activity:

2

Now to look deeper and I’ll show my way of using different tools to solve these issues at different stages, using mostly Sysinternals tools.

I started Process Explorer (procexp.exe) and added in the below fields:

select colums 3

 

 

 

 

 

 

 

 

 

 

 

 

 

Then sorted by Disk Writes and looked at the process associated, note this isn’t an actual screenshot from the server as I only saved the .pml file from the procmon.exe trace:

4

 

So at that time I knew that from the procexp.exe results that one of the httpd.exe processes, the child process of the primary httpd.exe process was writing a lot of new files to the directory below:

5

 

Now I moved to Process Monitor (procmon.exe) probably the most widely used Sysinternals tool. As I knew what process to look for, I set a trace going for 5 minutes then stopped and filtered by PID 544 and then added in filters to include Operation=Is=WriteFile and Operation=Is=ReadFile. Now this proved that this activity was writing .php files in batches to the \public directory but also there was a lot of information so I cleared those filters and set Path=Contains=\Apache2.2\htdocs\templates_c\public to see all results for that path, again popped up httpd.exe 544 again along with the usual process of explorer.exe.

You can see the quick succession of the file creations periodically, though the reason as to why it’s creating files in these directories is unknown. So to satisfy our suspicions that the httpd.exe PID:544 is creating the files we stopped the httpd.exe service (not recommended if you’ve got a popular website, obviously) to see that the file creations stopped, and they did.

So it was clearly this process that was creating the files but why exactly? I then decided to look at the call stack of one of the writefile events to see if there was any .dlls being called that either out of the ordinary or suspicious, funnily enough I found the php5ts.dll:

6

 

Notice I haven’t configured symbols but looking at this trace it provided the suspect straight away, also looking at the trace modules I can see the particular .dll and its location:

7

 

So now we knew that it was potentially a PHP script that was creating the files, maybe would have been more clear if I’d configured symbols so I could see the functions though I’d found enough info. We contacted the web developers and asked if they’d configured any PHP scripts that would create batches of these files and they advised there was such a script that should be disabled in the production environment that may have not been disabled. This particular scripts create log files in .php formats every time a user visits the site and of course this script was enabled. It was then disabled and the scripts stopped and the disk I/O returned to acceptable levels.

Advertisements

vCloud Director 101

I decided to write this blog (read it in reference to my slideshow) to give you guidance on the complex terminologies of VMware vCloud director. I will refer to it vCD from now on to save my poor fingers.

If you’re a vSphere admin, vCD terminology is very different, it uses new terms to label layers, a way to image this is an onion ring, as you peel away the layers you get to the core or centre of the onion, vCD is abstraction layer above your infrastructure. It hides all the bits and pieces your users don’t need to see, and you don’t want them to mess around with!

Massimo gave a great quote. Check out his blog for all things vCD. He wraps it up in this quote.

“Think about how difficult it is to implement something that allows and end-user to create, in self-service mode, separate layer 2 network segments, define custom layer 3 IP policies, configure services such as DHCP, NAT and Firewall… all without having to ask the vSphere / cloud administrator to do all that for you, all without messing up with the cloud-wide setup, all without causing conflicts with the other tenants on the cloud. This is a titanic effort, believe me.”

This blog will not go through the install of vCD, as it is beyond the scope of this article, but have a look over at Kendrick Coleman’s blog site, as he has a fantastic walkthrough on a vCD install. Now let’s tackle the terminology you need to understand, these terms are prompted by the wizard once installation has completed and you’re ready to create your first tenant.

So as my vCD slide outlines, what is vCloud Director, it’s the wrapper around your vSphere infrastructure, it hides the complex bits and automates creation of VM’s and networks without admin intervention.
What is a vCD Cell?

An instance of vCloud Director

Can be scaled by adding multiple cells behind a load balancer

Scales up to 10,000 VMs and 25 vCenter Servers

Creates virtual datacentres by pooling resources into new units of consumption

Secures and Isolates users with vShield, LDAP and RBAC with policies

Components of a vCD Deployment

Min 2xESXi hosts vSphere ENT or ENT+

No Enterprise Plus licence means No vCDNI networking

Shared Storage for DRS of hosts

vCenter

vCloud Director (VM)

Embedded or remote DB

AD / LDAP Directory

vShield Manager VM

vShield Edge VMs (automatically deployed on ESXi hosts)

vApps, deployed on ESXi hosts

Optional Components

VMware Chargeback

Meter the consumption of VM’s, networks etc., and bill them.

vCloud Connector

Connect Private Clouds to public, makes the interchange of VMs across clouds seamless.

vCD Logical Terminology:

Provider virtual Data Centre (PvDC): A logical grouping of vSphere compute and storage resources where all resources are equal (some clouds may have tiers with platinum/gold/silver)

Organisation: A unit of administration with its own users, groups, policies, and catalogues. An Org has its own security boundary. These are ‘tenants’.

Organisation vDC: A logical grouping of resources from one of more provider vDCs, enabling different performance, SLA, and cost options to be available in the same organisation.

Recommendations

Allocate at least one vCloud Director (Cell) for each vCenter server

Configure the vCloud Director database, VMware appliance is for testing purposes and uses embedded Oracle DB, not for production (16GB Ram, 100GB Storage, 4vCpus)

Read the vCat documentation to see how See VMware recommends building vCloud Director.

Recommended Configuration

Create 2 Clusters, 1 for management and 1 for resource, you don’t want your new cloud to be consuming resources before you have even installed any tenants onto it yet would you?

Create all the VMs needed for management in the management cluster.

Layers of Networking

Customer/Tenant/Organisation Network Layer (Completely Dynamic – No configuration by the customer)
————————————————————————————–

vCloud Director Network Layer

Maps to components of vSphere layer and physical layer

vSphere Network Layer

vSwitches, Port Groups etc. (must be stable and static)

Physical Network Layer

Switches/routers and IP’s etc. (must be stable and static)

vCD Networking Terms:

External Network

The vCD inner networking component is called External Networks. If you want your Organization (and in turns your vApps) to have connectivity to the external world you need to have External Networks. As the word implies, these are networks that are managed by someone that is typically external to the vCD environment and are identified by a vSphere Port Group. That’s in fact what you do when you create a vCD External Network: you point to an existing vSphere Port Group. Essentially you are telling vCloud Director that there is a Port Group that is able to provide external connectivity to your cloud environment. The typical example is a Port Group with VLAN 233 (for instance) which can support native Internet traffic. For naming convention you will be calling this External Network something like Internet or Ext-Net-Internet. I usually suggest naming the vCD External Network after the vSphere Port Group for ease of tracking.

• Connects vCD to the outside world

• Based on a vSphere port group
NOTE

When you create the port group on the dvSwitch recommended editing settings to make the ports Ephemeral – no limit on ports

Organisational Network

External Networks are easy. With Organization Networks things start to become more “interesting”. In the previous section we have created cloud-wide external connectivity (i.e. External Networks). Now we are zooming inside an Organization. An Organization (or Org) is a logical construct within vCD that describes a tenant or a customer. Cloud end-users are defined inside each Organization.

• A virtual network for tenants / customers

• Communicate with each other and access the internet

• Require an External network, network pool or both

The 3 Types of Org network a tenant can have are:

• External Organisational network: Direct

• External Organisational network: NAT-routed

• Internal Organisational network (private)

3 types of network pools you can allocate to tenants:
VLAN Backed (flexible, no special MTU settings, requires a lot of VLAN management)

Network Isolation Backed (vCDNI – no VLAN ranges to track, must change MTU / mac-in-mac encapsulation)

vSphere Port Group Backed (Standard and Distributed, no auto network deployment – most work involved)

Ideally you need to use vCDNI, so everything is automated, but you will need an Enterprise Plus licence for this feature, and also make sure that the MTU settings are set higher than 1500 at the physical switch level, esx host level and vCenter server level. You can use as high as 9000 without causing problems.

Network Pools

At this point you may have an overall understanding of what a Network Pool is and why it is used. In summary it is a small CMDB that contains layer 2 segments available to vCD administrators and end-users. Note Network Pools need to be created before we start deploying the actual networks we have described above (with the exception of the External Networks because they don’t use Networks Pools).

So far we kept referring to a “layer 2 segment” as a Port Group with an associated VLAN id. This is correct but it doesn’t tell the whole story. There are really three different types of Network Pools one can create.

VLAN-backed Network Pools: this is the easiest to get. You can, for example, create a Network Pool and give it a range of VLAN ID 100 to 199. Whenever you grab one of these IDs because you need to deploy a new layer 2 segment, vCD will tell vCenter “please create on the fly a Port Group, and give it VLAN ID 100″. The next time there is a need for another layer 2 segment vCD will tell vCenter “please create on the fly a Port Group, and give it VLAN ID 101″. And so on. Of course if one of these networks is destroyed during the lifecycle of the cloud, the corresponding VLAN ID gets put back into the pool of available networks to be deployed.

Port Group-backed Network Pools: it is similar to the VLAN-backed. The difference is that the Port Groups need to be pre-provisioned on the vSphere infrastructure and they need to be imported into vCloud Director. So vCD won’t tell vCenter to create these on the fly, they are already there pre-provisioned. Why using this? Well there are some circumstances where vCenter cannot easily (programmatically) create Port Groups on the fly. This is the case when you use vSphere Standard Switches (as opposed to Distributed Switches) or when you use the Nexus 1000v (at the moment vCD cannot manipulate programmatically Port Profiles).

vCloud Director Network Isolation Network Pools: This is when things start to get interesting (again). We use a technique called Mac-in-Mac to create layer 2 separated networks without using VLANs. Yeah that’s right. This is extremely useful for big environments where VLAN management is problematic, either because there is a limited number of VLANs available or because keeping track of VLANs is a big management overhead (especially if you use an excel spread sheet to do that ).

When you create such a Network Pool you only specify how many of these layer 2 networks you want this Network Pool to have and you are done. When vCD starts to deploy Port Groups from this Network Pool you won’t see any VLAN associated to them but they are indeed different layer 2 segments.

Now the acronym VCD-NI and the labels Preprovisioned and Created-on-the-fly in the pictures above should make more sense to you. Try to go back and have a look at them again.
Virtual Machines IP management

First of all note you cannot connect a vNIC to an External Network directly. You can however connect the vNIC to either an Organization Network or a vApp Network.
Now the question is: what happens when you connect a vNIC to either an Organization Network or a vApp Network? How do you control the layer 3 behaviour? As we said, you have a choice of connecting each vNIC of the VM to an Organization Network, a vApp Network or leave the vNIC not connected.
Reference URL’s
Massimo
http://it20.info/2010/09/vcloud-director-networking-for-dummies/

Duncan Epping – Creating a vCD Lab on your Mac/Laptop
http://www.yellow-bricks.com/2010/09/13/creating-a-vcd-lab-on-your-maclaptop/

Chris Colotti – VMware vCloud “In a Box” for your Home Lab
http://www.chriscolotti.us/vmware/vsphere/vmware-vcloud-in-a-box-for-your-home-lab/

vCloud networking explained in 1 slide and 52 animations
http://www.ntpro.nl/blog/archives/2024-vCloud-networking-explained-in-1-slide-and-52-animations.html