www.facebook.com/prpass san basics for dbas joey dantoni sql saturday #106 san juan, pr
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SAN Basics for DBAs
Joey D’Antoni SQL Saturday #106 San Juan, PR
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About Me
Principal Architecture SQL Server at Comcast Blog: joedantoni.wordpress.com Twitter: @jdanton Email: [email protected]
Storage
Understanding Storage Types A little bit about SSDs RAID Levels Components of a SAN SAN Benefits SANs and DR Summary
Storage
Different Kind of Storage
Hard Drive Components
Caching
Almost all hard drives (SAN, standalone) 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!
Why is storage the bottleneck?
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
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
CPU and Disks
As CPUs have gotten faster they have the ability to drive more IOPs.
Modern CPUs are so powerful they can saturate a 10 GB connection with I/O requests—your disks can’t possibly keep up
SSDs (Solid State Drives)
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
SSDs are Expensive
List Prices From Fusion-IO160GB 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
RAID
RAID—Redundant Array of Independent Disks
Hard Drives Will Fail, RAID is what gives you protection from that
RAID 0
RAID 0, Don’t Do This
From a major virtualization vendor benchmark
RAID 0
No data protection at all
Best performance If you lose one disk,
you lose it all As you add disks
risk increases
RAID 1--Mirroring
Mirroring No increase in
write performance Read
performance is increased
50% Capacity Loss
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
BAARF
RAID 1+0 (10) Mirrored Striping
Best performance Requires 4 or more
drives Only 50% of actual
capacity is used
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!!!
Storage Area Network
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
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)
iSCSI vs Fibre Channel
iSCSI is cheaper, and in smaller shops your network admin can manage the switches
Over 10G Ethernet iSCSI is faster, but that is still uncommon
Fiber is more susceptible to breakage, but currently more common
Fibre is faster, generally Note—all SAN components must be the same
speed, or network traffic reverts to slowest in chain
Multi-Pathing
How your SAN admin sleeps at night!
Make sure your databases servers are multi-pathed
SAN Throughput
1 GB iSCSI
4 GB FC
8 GB FC
10 GB iSCSI
0 200 400 600 800 1000 1200 1400
Max Mb/S
Max Mb/S
What are the Benefits of a SAN
Expand Capacity easily and on the fly High availability Disaster Recovery
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—Fiber Optic connection to SAN
HBA Card—Card that plugs into your server to connect it to the SAN
IOPs—I/O Operations Per Second—the way your SAN admin measures performance
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
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
SAN Replication
Shared Environment vs Dedicated Environment
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….
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
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
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
Test Your SAN
Good free tools available like SQLIO Never run this on a production server (and
warn your SAN admin)
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
Questions?
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