Overview of Storage and SAN topics for DBAs. Presented to Central Pennsylvania SQL Server Users group on November 13, 2012.

1. SAN Basics for DBAs
Joey D’Antoni
Central Pennsylvania User Group
November 13, 2012
www.facebook.com/prpass

2. About Me
 Principal Architect SQL Server at Comcast Cable
 Blog: joedantoni.wordpress.com
 Twitter: @jdanton
 Email: jdanton1@yahoo.com

3. Storage
 Understanding Storage Types
 SSDs
 RAID Levels
 Components of a SAN
 SAN Benefits
 SANs and DR
 Summary

4. Storage

5. Different Kind of Storage

6. Hard Drive Components

7. Caching
 Almost all hard drives (SAN, Direct Attached)
have some form of caching (RAM in front of
storage)
 For SQL Servers—make sure you have a
battery backed cache—if you don’t and
power fails—you will lose data!

8. Disk Drives
 Hard Drives can only spin at 15,000 RPM.
 Hard Drive Performance has improved
approximately 50x
 Have grown in capacity
 During the performance improvement CPU
speed increase 5521x

9. Why is storage the bottleneck?

10. Memory versus Hard Drives

11. Latency
 ―Disk latency is around 13ms, but it depends on the
quality and rotational speed of the hard drive. RAM
latency is around 83 nanoseconds. How big is the
difference?
If RAM was an F-18 Hornet with a max speed of 1,190
mph (more than 1.5x the speed of sound), disk access
speed is a banana slug with a top speed of 0.007 mph.‖
--credit Christian Paredes Blue Box Group

12. SSDs (Solid State Drives)

13. SSDs are Fast
 Much faster on random reads and writes
 At least 5x better performance, often much more
 Up to 350x faster on seeks
 Not nearly as much of difference on
sequential reads and writes

14. SSDs are Expensive
 List Prices From Fusion-IO
160GB SLC ioDrive - $8495
320GB SLC ioDrive - $15495
320GB MLC ioDrive - $7495
640GB MLC ioDrive - $11495
320GB SLC ioDrive Duo – 16,990
640GB SLC ioDrive Duo - $30,990
640GB MLC ioDrive Duo - $14,990
1.28TB MLC ioDrive Duo - $22,990
 These are really great for TempDB

15. SANs and SSDs
 More to come later!

16. RAID
 RAID—Redundant Array of Independent
Disks
 Hard Drives Will Fail, RAID is what gives you
protection from that

17. RAID 0

18. RAID 0, Don’t Do This
 From a major virtualization vendor
benchmark

19. RAID 0
 No data protection
at all
 Best performance
 If you lose one disk,
you lose it all
 As you add disks
risk increases

20. RAID 1--Mirroring
 Mirroring
 No increase in
write performance
 Read
performance is
increased
 50% Capacity
Loss

21. RAID 5—Striping (What you SAN Admin Wants)
 Maximum Capacity
 Big Write Penalty—
gets worse as more
disks are added
 Not good for highly
transaction
databases
 *Caveat

22. RAID 1+0 (10) Mirrored Striping
 Best performance
 Requires 4 or more
drives
 Only 50% of actual
capacity is used

23. Summary of RAID Levels
 Ask for RAID 10 for Everything (you won’t get
it)
 Make sure your TempDB and Logs are on
RAID 10
 NEVER USE RAID 0!!!

24. Storage Area Network

25. What is a SAN?
 Basically a specialized computer for storage
 Computer, Switches and Hard Drives
 Not a performance device
 Can be used for redundancy and DR
purposes
 Will serve many servers—so critical piece of
your infrastructure

26. SAN Components
 HBA (Fibre) Card—Connects your server to SAN
via Fiber Optic cable
 iSCSI Card—Ethernet Card connecting server to
SAN
 Switch—Either fibre or ethernet switch
connecting server to SAN
 SAN head unit—Controls processing, RAID
levels
 Disk Array—The physical array behind your SAN
(a bunch of hard drives)

27. SAN Terms
 LUN—Logical Unit Number, but in practical
terms, what your SAN admin will call a disk
that he presents to your server
 Fibre Channel—Cable connection to SAN
 IOPs—I/O Operations Per Second—the way
your SAN admin measures performance

28. iSCSI vs Fibre Channel
 iSCSI is cheaper, and in smaller shops your
network admin can manage the switches
 Over 10G Ethernet iSCSI is faster, unless…
 16 GB FC is still uncommond
 Fiber is more susceptible to breakage, but
currently more common
 Note—all SAN components must be the
same speed, or network traffic reverts to
slowest in chain

29. Multi-Pathing
 How your SAN
admin sleeps at
night!
 Make sure your
databases
servers are
multi-pathed

30. SAN Throughput
Max Mb/S
10 GB iSCSI
8 GB FC
Max Mb/S
4 GB FC
1 GB iSCSI
0 200 400 600 800 1000 1200 1400

31. What are the Benefits of a SAN
 Expand Capacity easily and on the fly
 High availability
 Disaster Recovery

32. SANs and SQL Server—What to ask for
 TempDB absolutely needs its own disk (and
you should have multiple TempDB files)
 Logs should be on a separate disk from data
files
 Ideally separate system and user DBs
 If shared instance, put split high utilization
DBs onto separate disk devices

33. SANs and DR—Block
 WARNING!—Don’t try this unless you have a
real budget and a good SAN admin
 Most SANs vendors have as an option SAN
replication
 Allows for multi-site failover
 Multi-site clustering fully supported in SQL
Server 2012
 Expensive—requires fiber connection
between sites and expensive software

34. SAN Replication

35. Shared Environment vs Dedicated
Environment

36. SANs are Multi-Tenant
 You don’t want to share disks with the
Exchange server
 File servers are a decent partner for
database servers
 But….

37. If you have are on a new SAN
 Most of the previous slides, don’t matter
 This technology on applies to really high
end, enterprise-class storage arrays
 IBM, EMC, Hitachi

38. EMC VMax Fast DP
 Allows for dynamic moves of disk from faster
to slower disks (Fibre channel to SATA), or
slower to faster (FC to SSD)
 Totally dynamic, and seamless to servers
 Moves data in 768k extents
 Your SAN admin doesn’t know where your
data is

39. FAST VP
Data
SSD SSD SSD
15K Fibre Channel 15k Fibre Channel 15k Fibre Channel
Log
10K SATA 10K SATA 10K SATA

40. What does this mean for the DBA?
 Overall—don’t worry too much about—the
technology is solid
 Make sure your transaction logs are in a
group that can not go to SSD.
 A lot of what we did in the past, changes with
this technology

41. Test Your SAN
 Good free tools available like SQLIO
 Never run this on a production server (and
warn your SAN admin)

42. Summary
 RAID 0 is bad
 Hard Drives will always be the bottleneck
 Be nice to your SAN admin—ask for RAID 10
 Split your SQL files across many disks
 SSDs are fast, but pricey

43. Questions?

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45. Contact Info
 Twitter: @jdanton
 Email: jdanton1@yahoo.com
 Blog (slides): joedantoni.wordpress.com