Myth Busting Goes Virtual

1. Myth Busting Goes Virtual Todd Mera - Todd.Mera@Quest.com Systems Engineer | Quest Software Server Virtualization Management Group (541) 314-3302 Mattias Sundling Evangelist, Quest Software Eric Sloof VMware Certified Instructor, NTPRO.NL

2. Just in case you are curious… • 2010 – With the second launch of the SpaceX Dragon, SpaceX becomes the first privately held company to successfully launch, orbit and recover a spacecraft. • 1995 - The Grateful Dead announced they were breaking up after 30 years of making music. The news came four months after the death of lead guitarist Jerry Garcia • 1886 – Diego Rivera, Mexicanpainter (d. 1957) • Eli Whitney (December 8, 1765 – January 8, 1825) was an American inventor best known for inventing the cotton gin • 1966 – Sinéad O'Connor, Irish musician

3. Introduction vSphere evolves with every release. Things that used to be true aren't true anymore. Engage in virtualization communities and social media to get up to speed.

4. Agenda/Myths iSCSI RDMs have superior performance over VMFS. CBT causes significant overhead on your VMs. Resource Pools should always be used to categorize and allocate resources to VMs. LSI SCSI is always better than ParavirtualSCSI.

5. Myth 1:iSCSI RDMs have superior performance over VMFS

6. What is a RDM RAW LUN VMFS volume A RDM is a symbolic link. When a LUN is opened for access, the mapping file is read to obtain the reference to the raw LUN. Thereafter, reads and writes go directly to the raw LUN rather than going through the mapping file.

7. VMkernel and Storage Physical Compatibility mode RDM Virtual mode RDM Regular VMDK on VMFS Logical device IO scheduler vStorage APIs Adapter IO schedulerand Linux emulation

8. The iSCSI Laboratory Iomega StorCenter px6-300d with 6 SATA 7200 Disks Windows 2008 R24096 MB – 1 vCPUHardware Version 8 VMware vSphere 5 Single Intel 1GB Ethernet Cisco 2960 switchMTU Size 1500

9. Results Passmark PerformanceTest RDM Physical RDM Virtual VMDK on VMFS Microsoft software ISCSI initiator

10. Myth Busted 1 Gigabit/sec (Gbps) = 112.16 MB/s. Use VMFS datastores whenever possible. VMFS is optimized for storing and accessing large files. Only Use RDMs if your VM is performing SAN snapshotting. is clustered to a physical machine using MSCS. has large amounts of data (64 TB) that you do not want to convert into a VMDK (2 TB).

11. Myth 2:CBT causes significant overhead on your VMs

12. What is CBT? CBT Driver Driver inside VMkernel Identifies change blocks within virtual disks Block size based on VMDK size Backup window and host resources significantly reduced Requirements: vSphere4+ and Virtual HW v7+ Limitations: pRDM, iSCSI within VM Enable through vCenter or backup application (per VM)

13. CBT overhead • Memory • Max 256 KB / Disk (2TB) • 1.25 KB / 10 GB VMDK • CPU • Turning on a bit in bitmap when an I/O request completes • Storage • Space • One .ctk file per VMDK • .ctk file 0.5 MB /10 GB VMDK • I/O • Every time disk gets closed, change tracking info written to disk

14. Test/Result CBT Enabled CBT Disabled Very little overhead CPU, Mem, Storage Could not measure it, except .ctk file No negative impact on disk I/O

15. Myth Busted CBT overhead is very small Backup window and host resources reduced significant Always use CBT if your backup solution supports it

16. Myth 3:Resource Pools should always be used to categorize and allocate resources to VMs

17. Resource Settings CPU – Shares, Reservation, Limit. Memory – Shares, Reservation, Limit. vApp Resource Pool VM

18. Sibling CPU Shares Value vApp = 4000 Resource Pool= 4000 VM = number of vCPU * 1000

19. Sibling Memory Shares Value vApp = 163840 Resource Pool = 163840 VM = Mem MB * 10

20. The Laboratory RP 4000 Shares 6 Ghz RP 4000 Shares 6 Ghz vApp 4000 Shares 6 Ghz VM 4000 Shares 6 Ghz 6 Ghz 0,75 Ghz 0.5 Ghz 1.5 Ghz Root Resource Pool 24 Ghz 6 Ghz 6 Ghz 6 Ghz 6 Ghz

21. Myth Busted If you want to use Resource Pools, do your math! group VMs in a container use the blue folders!

22. Myth 4:LSI Logic SCSI is always better than PVSCSI

23. What is PVSCSI? • Supports only Win 2003+, RHEL5+, SUSE Linux Enterprise 11 SP1+, Ubuntu 10.04 +, Linux 2.6.33+ • Virtual HW v7+ • Paravirtual SCSI • Introduced in vSphere 4, improved in vSphere 4.1 • Designed for high performance (+12%) • Requires less resources on vSphere Host (-18% CPU)

24. Test Result LSI Logic vs. PVSCSI LSI Logic PVSCSI • Very similar disk throughput • Lower Host CPU Utilization for PVSCSI Host CPU utilization 90MB/s – 60 000 IOPS

25. PVSCSI Limitations • PVSCSI controllers have the following limitations: • Disks on PVSCSI controllers might not experience performance gains if they have snapshots or if memory on the ESXi host is over committed. • MSCS clusters are not supported. • PVSCSI controllers do not support boot disks, the disk that contains the system software, on Red Hat Linux 5 virtual machines. Attach the boot disk to the virtual machine by using any of the other supported controller types. Source: http://pubs.vmware.com/vsphere-50/index.jsp?topic=/com.vmware.vsphere.storage.doc_50/GUID-8AE88758-20C1-4873-99C7-181EF9ACFA70.html

26. Myth Busted PVSCSI is equal or faster than LSI SCSI PVSCSI requires less Host resources Used to have more limitations PVSCSI is better in all ways so why aren´t we using it on all supported VMs? Takes time to change behaviour

27. Summary VMFS is better than RDMs CBT has very little overhead Do your math when using sibling RPs PVSCSI is equal or faster and requires less resources than LSI SCSI

28. Thanks!