Storage 1 Storage 101 What is a storage

Storage 1

Storage 101 What is a storage array?

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

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 • i. SCSI – Internet SCSI • SCSI – • FC – Fibre Channel • FCo. E – 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.

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

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SAN Fabric Details • A SAN Fabric has hosts that connect to the network – Each host has a physical connection and some logical addresses § p. WWN (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 11 v 2 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 8

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

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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 i. SCSI, FC, or FCo. E – 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

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.

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

Physical Disks • These days physical disks come in all shapes and sizes – Spinning drives come in capacities of anywhere from 146 GB to 3 TB, 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 15000 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 960 GB 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.

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 15

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 § 15 k 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.

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 16 Gb full duplex, though 8 Gb is more common – That’s 3200 MBps in each direction, transferring 3 GB of data each second in one direction or 6 GB of data bi-directionally. • FCo. E currently supports 10 Gb, though the roadmap includes 40 Gb and 100 Gb – 10 Gb is 2400 MBps in each direction, while 100 Gb is 24000 MBps, 23. 4 GB per second! • Besides the speed is the matter of oversubscription

Performance • Oversubscription – The practice of providing less aggregate bandwidth than the environment may add up to • In an environment with 100 servers having dual 8 Gb FC connections we’d have a total of 1600 Gb that is directed at a storage array via some SAN switch • The storage array may only have a total of eight 8 Gb FC connections for 64 Gb 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

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 19

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. 20

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 S 3, or simple storage service § It just so happens by default anything stored in S 3 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. 21