SQL Server On SANs

SQL Server onStorage Area Networks

Brent Ozar
SQL Server MVPfor Quest Software
Managed SQL, VM, 80tb SAN for $7b co
Published author
Made lots of expensive mistakes
www.BrentOzar.com
@BrentO on Twitter

BrentOzar.com/go/insidetheblackbox

The Agenda
Inside the SAN
DBA Pros & Cons
Starting From The Beginning
How to Use SQLIO
Multipathing

In The Beginning…

Next: External Storage

Storage Area Networks
Independent
Expandable
Well-Protected
Blazing Fast
Complex
Expensive

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SAN Components
Drive enclosures
Controllers (& Cache)
Switch networks
Host Bus Adapters
HBA Drivers
Servers

Drive Allocation Methods

Good Things
Clustering
Table partitioning
Faster builds
Easier growth
Caching speed
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Not-So-Good Things
Black box
Cachingmay not help
Compatibility lists
More drivers
Tough to grow
SAN adminsmay not help
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“How many gigs do you need?”

“We’ll keep an eye on it for ya.”
Perfmon changes
Neighbors change
SAN changes
SAN monitoring software is tough
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What’s Your Bottleneck?
Not Enough Drives
Drives Too Slow
Shared Drives
RAID Level
SAN Controllers
Partition Alignment
Drivers
Multipathing

Things to Monitor
Hard drives
Controllers (CPU, caching)
Controller connectivity to the network
Network switch throughput
Server connectivity to the SAN (the HBA)
Server drivers

The X Factor: Redundancy
Hard drives – hundreds
Controllers – 2+
Controller connectivity to network – 4+
Network – separate networks, switches
Server connectivity to SAN – 2+
Network fabrics – iSCSI, Fiber, WAN

SAN Monitoring
Strict HCLs, SCLs
Cross-platformmeans JAVA
No “full” picture
Very, very, veryexpensive
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Unpredictable, Unexplainable

Start From The Beginning
Get block sizes right
Align partitions
Design for pathing
Test with SQLIO
Install SQL Server
Monitor sec/read, write
Save history

Simple SAN Pathing

SIMPLE?!?1#%&@!?

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Goals of Multipathing
Protection
Performance

Active/Active Can Mean

Active/Active Gotchas
One path per LUN/volume
Sending vs receiving
Post-failover stickiness
Network design

Network Bottleneck Example

Pathing Really Matters Now

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Why Can’t We Go Faster?

How to Run SQLIO
sqlio -kW -t2 -s120 -dM -o1 -frandom -b64 -BH -LS Testfile.dat

Write This Down. It’s Important.

We Did the Hard Work

The Output
E:Program Files (x86)SQLIO>sqlio -kW -t2 -s120 -dM -o1 -frandom -b64 -BH -LS Testfile.dat
sqlio v1.5.SG
using system counter for latency timings, -1361967296 counts per second
2 threads writing for 120 secs to file M:Testfile.dat
using 64KB random IOs
enabling multiple I/Os per thread with 1 outstanding
buffering set to use hardware disk cache (but not file cache)
using current size: 24576 MB for file: M:Testfile.dat
initialization done
CUMULATIVE DATA:
throughput metrics:
IOs/sec: 1539.50
MBs/sec: 96.21
latency metrics:
Min_Latency(ms): 0
Avg_Latency(ms): 0
Max_Latency(ms): 572
histogram:
ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+
%: 66 32 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Common Bottlenecks
1 gig = ~125 MB/sec
2 gig = ~250 MB/sec
4 gig = ~500 MB/sec
10 gig = ~1250 MB/sec

Working Around It
Data/logs/tempdbon different volumes
Separategroups of DBs
Separate DBinto filegroups
TempDB, backups
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Wrapping It Up
Test before deployment
Learn multipathing
Design DB files around SAN limits
Monitor forever
Get vendor help
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Advanced Topics
Table partitioning
Filegroups & files
Snapshot backups
Storage virtualization
Storage VMotion
SAN administration
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BrentOzar.com/go/insidetheblackbox