1. Storage

2. Storage 101
What is a storage array?

3. Agenda Definitions What is a SAN Fabric What is a storage array
Front-end connections
Controllers
Back-end connections
Physical Disks
Management
Performance
Future – Distributed storage

4. Definitions SAN – Storage Area Network
This is generally used as a catch all term for all the following definitions
For storage personnel SAN does NOT equal storage array
LUN – Logical Unit Number, also known as a volume
WWN – World Wide Name
MAC address for storage networks
Fabric – Network that connects hosts to storage
iSCSI – Internet SCSI
SCSI –
FC – Fibre Channel
FCoE – Fibre Channel over Ethernet
FCIP – Fibre Channel over IP
Storage Array – Storage Device that provides block level access to volumes
DAS/DASD – Direct Attached Storage
Storage directly attached to a server without any network
NAS – Network attached Storage
Storage device that provides file level access to volumes
RAID – Redundant array of Independent Disks
A way to combine multiple physical disks into a logical entity providing different performance and protection characteristics.

5. What is a SAN fabric
A network comprising hosts, storage arrays they access, and storage switches that provide the network connectivity

8. SAN Fabric Details A SAN Fabric has hosts that connect to the network
Each host has a physical connection and some logical addresses
pWWN (Port WWN) is the equivalent MAC address for the port on the host that is connected to the network
FCID is a dynamic address that represents the connection as well
Only HP-UX 11v2 and below use this
Typically hosts connect into some storage switch
These look like traditional network switches in many ways and operate the same way.
These switches will contain both host ports and storage ports, or in the storage world, initiators and targets
Storage arrays that provide storage also connect into these switches to provide the full network

9. What is a storage array?
A storage array is a system that consists of components that provide storage available for consumption
The components are front-end ports, controllers, back-end ports, and physical disk drives

11. Front-end connections
Front-end connections are used for individual hosts to connect to the storage array and utilize the volumes available
This can be directly connected in a small or medium size SAN, or in a DAS environment
The physical transport mechanism can be fibre or copper
The logical transport protocols can be block level protocols such as iSCSI, FC, or FCoE
Some arrays also support file level protocols as well such as NAS devices
The larger arrays tend to have more front-end connections to aggregate bandwidth and provide load balancing
Volumes are typically presented via one or more front-end connections to hosts

12. Controllers
Controllers are the brains that translate the request from the front-end ports and determine how to fulfill the request
Controllers run code optimized for moving data and performing mathematical calculations needed to support RAID levels
Controllers also have a certain amount of on-board memory, or cache, to help reduce the amount of data that has to come from spinning disks.
Many arrays perform some level of read-ahead caching and write caching to optimize performance
They also have some diagnostics routines and management in order to support the operations of the array.

13. Back-end connections
From the controllers themselves to the physical disk shelves or disks there are back-end connections.
These send actual commands to the disks commanding them to retrieve or write blocks of data.
These connections are usually transparent to all but the most sophisticated storage engineer.
Often times these have specific fan-out ratios where each disk shelf may have two or four connections and split the bandwidth available in some way.
Back-end connections are rarely a bottleneck

14. Physical Disks These days physical disks come in all shapes and sizes
Spinning drives come in capacities of anywhere from 146GB to 3TB, with the space increasing year over year (though not performance)
These drives also come in various rotational speeds anywhere from 5400 RPM in a laptop drive to RPM in an enterprise class drive, which directly affects performance
Non Spinning drives, also known as SSD’s, come in capacities that don’t yet match spinning drives, though there are SSD cards that have up to 960GB of storage space available.
These physical disks directly impact the performance of the storage array system, and are usually the bottleneck for most enterprise class storage systems.

15. Provisioning Provisioning storage is a multi-step process
Configure the host with any software including multi-path support
Alias the host port WWN
Zone the host port alias to a storage array WWN
Activate update zone information
Create host representation on storage array
Create volume on storage array
Present/LUN Mask volume to correct host
Format volume for use

16. Performance
There are many statistics you can use to monitor your storage devices, however there tend to be two key ones that directly impact performance more than most.
IOPS – Input/Output Operations Per Second
This is based on the number of disks that support the volume being used and the RAID level of the volume
15k RPM disks provide 200 IOPS raw without any RAID write penalty
Raid 1 has a 1:2 ratio for writes. For every 1 write command sent to the array, 2 commands are sent to the disks.
Raid 5 has a 1:4 ratio, while Raid 6 has a 1:6 ratio
Read existing data block, Read Parity 1, Read Parity 2, Calculate XOR (parity) is not I/O, Write data, Write Parity 1, Write Parity 2
Read commands are always 1:1
For an application that has a requirement of 10,000 IOPS and a 50/50 read to write ratio on a raid 6 volume:
5,000 read IOPS, translating into 25 physical disks
5,000 write IOPS translating into 30,000 back-end operations requiring 150 physical disks
Total requirement is 175 physical disks just to support the performance needed!
Bandwidth
This is based on the speed of the connections from the host to the array as well as how much oversubscription is taking place within the SAN Fabric.

17. Performance Bandwidth
This is based on the speed of the connections from the host to the array as well as how much oversubscription is taking place within the SAN Fabric.
Fibre Channel currently supports 16Gb full duplex, though 8Gb is more common
That’s 3200 MBps in each direction, transferring 3GB of data each second in one direction or 6GB of data bi-directionally.
FCoE currently supports 10Gb, though the roadmap includes 40Gb and 100Gb
10Gb is 2400 MBps in each direction, while 100Gb is MBps, 23.4GB per second!
Besides the speed is the matter of oversubscription

18. Performance
Oversubscription – The practice of providing less aggregate bandwidth than the environment may add up to
In an environment with 100 servers having dual 8Gb FC connections we’d have a total of 1600Gb that is directed at a storage array via some SAN switch
The storage array may only have a total of eight 8Gb FC connections for 64Gb aggregated bandwidth
We have a ratio of 1600:64 or 25:1.
This is done in networking all the time and is now a standard in the storage world.
The assumption is that there will never be a need for all 100 hosts to be transmitting 100% of the time their full bandwidth

19. Storage Futures Converged Infrastructure
Datacenters designed today talk about converged infrastructures
One HP Blade enclosure can encompass servers, networking, and storage components that need to be configured in a holistic manner
Virtualization has helped speed this convergence up, though organizational design is usually still far behind.
Storage arrays are beginning to support target based zoning
The goal is to reduce the administration needed to configure a host to storage mapping letting the storage array do more intelligent administration without human intervention

20. Storage Futures
Over the last few years storage has begun transitioning from “big old iron” to distributed systems where data is spread across multiple nodes for capacity and performance.
EMC Isilon
HP Ibrix
Nutanix
Vmware VSAN
Nexenta
As always in IT, the pendulum is swinging back to the distributed platforms for storage where each node hosts a small amount of data instead of a big platform hosting all of the data.

21. Storage Futures
Data protection is maturing from traditional RAID levels such as 1, 1+0, 5, 6, etc
RAID levels do offer additional protection however don’t protect against corruption most of the time
RAID levels also have performance implications that are usually negative to the applications residing upon them
These days the solution is to create multiple copies of files or blocks based upon some rules
Most of the large public cloud providers use this solution including Amazon S3, or simple storage service
It just so happens by default anything stored in S3 has three copies!
The ‘utopia’ world is a place where each application has some metadata that controls what protection level and performance characteristics are required
This would enable these applications to run internally or externally yet provide the same experience regardless.
This is the essence of SDDC, Software Defined Data Center. The application requirements will define where they run without any intervention.