1. Optimizing SQL Server Performance in a Virtual Environment
Denny Cherry
twitter.com/mrdenny

2. About Me
Denny Cherry & Associates Consulting 6 books Dozens of articles Microsoft MVP Microsoft Certified Master VMware vExpert

3. Topics of Discussion Diagnosing Performance Problems
Balloon Memory Drivers
Memory Deduplication Options
Storage Configuration Options

4. Tuning Differences in T-SQL
Nope
Nothing
Nope
Never
Nada
It’s all the same! No
Zero
Zip

5. Diagnosing Performance Problems
Check Host and Guest CPU numbers
Check Host for CPU thrashing
Check Host and Guest for Disk IO latency
For Thrashing
PerfMon in Hyper-V
esxtop in v-Sphere
%USED needs to be under 75%
Use SCVMM or vCenter to look at historical trends for these numbers
The storage is a very common place to see performance problems. If SQL Server is reporting slow IO via the DMVs or via the ERRORLOG file check IO latency numbers at the host and from the storage array. Look into auto-teiring options within the storage array to move hot portions of the disk to faster storage. Another option would be to use a dedicated LUN for the database instead of a shared LUN. The dedicated LUN could be connected to the guest via a Pass Through Disk in Hyper-V or a Raw Device Mapping in vSphere/ESX or via iSCSI directly to the guest.
If the Hypervisor host has limited bandwidth to the storage array, using a single iSCSI connection over a single 1 Gig-E network connection for example additional network links / faster network links may be needed. Moving from iSCSI to fiber channel may be required do to the lower latencys of fiber channel compared to iSCSI.
If iSCSI is being used review the network configuration to ensure that there are as few network devices between the server and the storage array as possible as each additional network device adds additional latency.

6. Balloon Memory Drivers
Used by host OS to request memory back from the guest OS
Prevents host of from paging physical memory to the hosts swap file
Should be enabled
Lock pages in memory should be disabled, unless enabled for a specific reason
Available in ESX 3.0+
Available in Windows Server 2008 R2 SP1+
Disabling the balloon drivers can cause memory pressure at the host level, which would be masked from the guest and cause performance issues.

7. Memory Reservations - VMware
Forces the memory to be available for the guest
Recommended that it be set to a portion of the allocated memory
For a sample machine with 64 Gigs of RAM, I’d recommend setting the memory reservation to Gigs (32 Gigs for SQL and 2-4 Gigs for Windows). This ensures that SQL will have enough memory in the event of a major system failure, to continue to function.

8. Memory Deduplication Options
Great for OS memory
Unless… multiple SQL Servers have the same pages in cache
Doesn’t work at all for SQL Server
Native in ESX since 3.0 or older
Introduced in Hyper-V in Server 2008 R2 SP1
Talk about what this process does, and why it’s so cool for other kinds of servers.
Talk about why it is so useless for SQL Servers.

9. Storage Configuration Options
IO is the same if the disks are physical or virtual
Use automatic tier adjusting technology if possible
Keep OS, data, logs, tempdb on separate disks if possible
VMDKs or vDisks only have a 1-2% performance penalty
Spend some time talking about FAST / Compellent automatic tier adjusting technology
FAST is available on CX4 running FLARE 34? Or newer DMX build
FAST is available on all VNX and VPLEX arrays (for a cost)
Also available on X-IO, 3PAR, etc.
Not all automatic tiering platforms are the same. Some more data faster than others from one tier to another. Some more data is bigger slices than others. EMC for example started by moving data in 8 Gig slides, but now uses 1 Gig slices. If you are running an older version of the EMC software upgrading may be worth it to remove the size of the slices so that the data can be moved between the tiers faster and with greater granualary.

10. Storage Deduplication
Can greatly improve overall performance
By deduplicating OS virtual disks, we save much less data to the array
As less data is written to the array, less OS data is loaded into cache on the array
Can increase risk of corruption
Data LUNs can’t be deduped very well
OS LUNs can be
Most array’s do not support this as it is very CPU intensive
Don’t forget to account for loss of deduplication as service packs and hot fixes are installed making files on different servers different

11. VMware Paravirtualization Driver
Optional Driver for vSphere Virtual Machines
Recommended for high IO workloads
Configured via VM Properties
Select SCSI Controller
Change Type

12. Monitor, Monitor, Monitor
Did I mention that you need to monitor
Watch all levels of the environment
SQL Server
Guest
Hypervisor
Host
Storage
Use SCVMM or vCenter for long term trending
Trust nothing
If your storage vendor charges extra for the monitoring tool, pay for it. It is worth the cost
Correlate Numbers Together

13. Some Perfmon Counters to Monitor
Reads & Writes / Sec
Seconds / Read & Write
Disk Queue
Page Life Expectancy
System Processor Queue
VM Disk (VMware)
VM Memory (VMware)

14. Thanks to our sponsors

15. Denny Cherry mrdenny@dcac.co www.dcac.co twitter.com/mrdenny

16. Thank for attending Singapore SQLSaturday#646!