PureStorage has 150TB DirectFlash Modules

I have just realized that PureStorage has 150TB DirectFlash Modules. 

That got me thinking. 

Flash capacity is increasing year by year. What are performance/capacity ratios?

The reason I'm thinking about it is that poor Tech Designer (like me) need some rule-of-thumb numbers for capacity/performance planning and sizing.

Virtual NIC Link Speed - is it really speed?

This will be a quick blog post, prompted by another question I received about VMware virtual NIC link speed. In this blog post I’d like to demonstrate that the virtual link speed shown in operating systems is merely a reported value and not an actual limit on throughput.

I have two Linux Mint (Debian based) systems mlin01 and mlin02 virtualized in VMware vSphere 8.0.3. Each system has VMXNET3 NIC. Both virtual machines are hosted on the same ESXi host, so they are not constraint by physical network. Let's test network bandwidth between these two systems with iperf.

How to troubleshoot virtual disk high latencies in VMware Virtual Machine

In VMware vSphere environments, even the most critical business applications are often virtualized. Occasionally, application owners may report high disk latency issues. However, disk I/O latency can be a complex topic because it depends on several factors, such as the size of the I/O operations, whether the I/O is a read or a write and in which ratio, and of course, the performance of the underlying storage subsystem. 

One of the most challenging aspects of any storage troubleshooting is understanding what size of I/O workload is being generated by the virtual machine. Storage workload I/O size is the significant factor to response time. There are different response times for 4 KB I/O and 1 MB I/O. Here are examples from my vSAN ESA performance testing.

• 32k IO, 100% read, 100% random - Read Latency: 2.03 ms Write Latency: 0.00 ms
• 32k IO, 100% write, 100% random - Read Latency: 0.00 ms Write Latency: 1.74 ms
• 32k IO, 70% read - 30% write, 100% random - Read Latency: 1.55 ms Write Latency: 1.99 ms
• 1024k IO, 100% read, 100% sequential - Read Latency: 6.38 ms Write Latency: 0.00 ms
• 1024k IO, 100% write, 100% sequential - Read Latency: 0.00 ms Write Latency: 8.30 ms
• 1024k IO, 70% read - 30% write, 100% sequential - Read Latency: 5.38 ms Write Latency: 8.68 ms

You can see that response times vary based on storage profile. However, application owners very often do not know what is the storage profile of their application workload and just complain that storage is slow. 

As one storage expert (I think it was Howard Marks [1] [2]) once said, there are only two types of storage performance - good enough and not good enough.

Fortunately, on an ESXi host, we have a useful tool called vscsiStats. We have to know on which ESXi host VM is running and ssh into that particular ESXi host.

The vSCSI monitoring procedure is

1. List all running virtual machines on particular ESXi host, and identify our Virtual Machine and its identifiers (worldGroupID and Virtual SCSI Disk handleID)
2. Start vSCSI statistics collection in ESXi host
3. Collect vSCSI statistics histogram data
4. Stop vSCSI statistics collection

The procedure is documented in VMware KB - Using vscsiStats to collect IO and Latency stats on Virtual Disks 

Let's test it in lab.

Are you looking for VMware SRM and cannot find it?

Here is what happened with VMware Site Recovery Manager. It was repackaged into VMware Live Recovery.

What is VMware Live Recovery?

VMware Live Recovery is the latest version of disaster and ransomware recovery from VMware. It combines VMware Live Site Recovery (previously Site Recovery Manager) with VMware Live Cyber Recovery (previously VMware Cloud Disaster Recovery) under a single shared management console and a single license. Customers can protect applications and data from modern ransomware and other disasters across VMware Cloud Foundation environments on-premises and in public clouds with flexible licensing for changing business needs and threats. 

For more details see the VMware Live Recovery FAQ and the VMware Live Recovery resource page.

In this blog post I will just copy information from Site Recovery Manager FAQ PDF, because that's what old good on-prem SRM is, and it is good to have it in HTML form in case Broadcom/VMware PDF from what ever reasons disapeer.

Here you have it ...

How to run IPERF on ESXi host?

iperf is great tool to test network throughput.There is iperf3 in ESXi host, but there are restrictions and you cannot run it.

There is the trick.

First of all, you have to disable ESXi advanced option execInstalledOnly=0. This enables you to run executable binaries which were not preinstalled by VMware.

Second step is to make a copy of iperf binary, because installed version os estricted and cannot be run.

The third step is to disable ESXi firewall to allow cross ESXi communication between iperf client and iperf server.

After finishing performance testing, you should clean ESXi environment

• delete your copy of iperf
• re-enable ESXi firewall to allow only required tcp/udp ports for ESXi services
  
• re-enable ESXi advanced option (execInstalledOnly=1) to keep ESXi hypervisor secure by default
  

ESXi Commands 

# Allow execute binaries which are not part of base installation

localcli system settings advanced set -o /User/execInstalledOnly -i 0
 

# Make a copy of iperf

cp /usr/lib/vmware/vsan/bin/iperf3 /usr/lib/vmware/vsan/bin/iperf3.copy

 

# Disable firewall

esxcli network firewall set --enabled false

# Run iperf server
./iperf3.copy -s -B 192.168.123.22

# Run iperf client (typically in another ESXi host than iperf server is running)
./iperf3.copy -c -B 192.168.123.22

After iperf benchmarking you should enable firewall and disallow execution of binaries which are not part of base installation

 

# Cleaning
rm /usr/lib/vmware/vsan/bin/iperf3.copy

esxcli network firewall set --enabled true
localcli system settings advanced set -o /User/execInstalledOnly -i 1

 

Test Jumbo Frames (MTU 9000) between ESXi hosts

When we want to enable Jumbo-Fames on VMware vSphere, it must be enabled on

• physical switches
• virtual switches - VMware Distributed Switch (VDS) or VMware Standard Switch (VSS)
• VMkernel interfaces where you would like to use Jumbo-Frames (typically NFS, iSCSI, NVMeoF, vSAN, vMotion)

Let's assume it is configured by network and vSphere administrators and we want to validate that vMotion network between two ESXi hosts supports Jumbo Frames. Let's say we have these two ESXi hosts

• ESX11 has IP address 10.160.22.111 on vMotion vmk interface within vMotion TCP/IP stack. 
• ESX12 has IP address 10.160.22.112 on vMotion vmk interface within vMotion TCP/IP stack.

Ping is a good network diagnostic tool for this purpose. It uses ICMP protocol within IP protocol. So, what is the maximum size of IP/ICMP packet? With Jumbo Frame we have 9000 bytes for Layer 2 (Ethernet Frame) payload and within Ethernet Frame is IP packet cariing ICMP packet with Echo Request. So, here is the calculation. 

9000 (MTU) - 20 (IP header) - 8 (ICMP header) = 8972 bytes

 

Let's do ping with 8972 bytes payload and with flag -d (fragmentation disabled).

[root@esx11:~] ping -I vmk1 -S vmotion -s 8972 -d 10.160.22.112
PING 10.160.22.112 (10.160.22.112): 8972 data bytes
8980 bytes from 10.160.22.112: icmp_seq=0 ttl=64 time=0.770 ms
8980 bytes from 10.160.22.112: icmp_seq=1 ttl=64 time=0.637 ms
8980 bytes from 10.160.22.112: icmp_seq=2 ttl=64 time=0.719 ms

We can see succesful test of large ICMP packets without fragmentation. We validated that ICMP packets with size 8972 bytes can be transfered over the network without fragmentation. That's the indication that Jumbo Frames (MTU 9000) are enabled end-to-end.

Now let's try to cary ICMP packets with size 8973 bytes.

[root@esx11:~] ping -I vmk1 -S vmotion -s 8973 -d 10.160.22.112
PING 10.160.22.112 (10.160.22.112): 8973 data bytes
sendto() failed (Message too long)
sendto() failed (Message too long)
sendto() failed (Message too long)

We can see that ICMP packets with size 8973 bytes cannot be transfered over the network without fragmentation. This is expected behavior and it proves that we know what we do.

Business Continuity and Disaster Recovery Terminology

Almost 10 years ago, I gave a presentation at the local VMware User Group (VMUG) meeting in Prague, Czechia, on Metro Cluster High Availability and SRM Disaster Recovery. The slide deck is available here on Slideshare. I highly recommend reviewing the slide deck, as it clearly explains the fundamental concepts and terminology of Business Continuity and Disaster Recovery (BCDR), along with the VMware technologies used to plan, design, and implement effective BCDR solutions.

Let me briefly outline the key BCDR concepts, documents, and terms below.

• Business Continuity Basic Concepts
• Resilience (High Availability)
• Recovery (Disaster Recovery)
• Mitigation (Disaster Avoidance)
• Business Continuity Essential Documents
• BIA (Business Impact Analysis) is essential document for any Business Continuity Initiative
  
• Risk Management Plan (Prevention and mitigation)
• Contingency Plan (Response and recovery)
• Business Continuity Basic Terms
• RPO (Recovery Point Objective) – Data level
• RTO (Recovery Time Objective) – Infrastructure level
• WRT (Work Recovery Time) – Application level
• MTD (Maximum Tolerable Downtime) = RTO + WRT – Business level
  

RPO (Recovery Point Objective) and RTO (Recovery Time Objective) are the most known terms in Business Continuity and Disaster Recovery world and I hope all IT professionals know at least these two terms. However, the repetition is the mother of wisdom so let's repeat what RPO and RTO are. The picture is worth 1,000 words so look at the picture bellow.

RPO and RTO

 

RPO - The maximum acceptable amount of data loss measured in time. In other words, "How far back in time can we afford to go in our backups?"

RTO - The maximum acceptable time to restore systems and services (aka infrastructure) after a disaster.

WRT - The time needed after systems are restored (post-RTO) to make applications fully operational (e.g., data validation, restarting services). It’s a subset of MTD and follows RTO.

MTD - How much time does our business accept before the company is back and running after a disaster. In other words, it is the total time a business can be unavailable before causing irrecoverable damage or significant impact.

Easy, right? Not really, Disaster Recovery projects are, based on my experience, the most complex project in IT infrastructure. 

Are you ready to support your business after the disaster and guarantee business continuity? Are you sure? 

 

Do you test your BCDR regularly? How often? Once a year? Twice a year? Or even more? 

 

Feel free to leave a comment.

How to check your public IP address from FreeBSD or Linux console

Web service available at https://ifconfig.me/ will expose the client IP address. This is useful when you do not know your public IP address as you are behind the NAT (Network Address Translation) in some public Wi-Fi access point or even in your home behing CGNAT (Carrier-Grade NAT) very often used by Internet Service Providers using IPv4.

How we can leverage it from FreeBSD? 

It is easy. Just use old good fetch command available on FreeBSD by default to retrieve a file by Uniform Resource Locator (URL).

Oneliner:

fetch -qo - https://ifconfig.me | grep "ip_addr:"

How we can leverage it from Linux? 

It is easy. I use Debian and there is old good wget command available by default. It can be used to retrieve a file by Uniform Resource Locator (URL) similarly to fetch on FreeBSD.

Oneliner:

wget -o /dev/null -O - https://ifconfig.me | grep "ip_addr:"

 

Conclusion

In Unix-like operating systems is very easy to leverage standard tools to get job done.