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
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
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
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!!!
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
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