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Components of a DS Storage Solution

Components of a DS Storage Solution. Ryan Leonard Storage and Solutions Architect. Agenda. Components of a DS3/4/5000 storage solution Physical vs. logical RAID levels. 3 main physical components. Storage Server Contains RAID controller(s) Power supplies, fan assemblies, etc.

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Components of a DS Storage Solution

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  1. Components of a DS Storage Solution Ryan Leonard Storage and Solutions Architect

  2. Agenda • Components of a DS3/4/5000 storage solution • Physical vs. logical • RAID levels

  3. 3 main physical components • Storage Server • Contains RAID controller(s) • Power supplies, fan assemblies, etc. • Expansion enclosures • Contains ESMs • Power supplies, fan assemblies, etc. • Disks • Where the data is actually stored

  4. Storage Server • Primary computational element • Generally composed of two RAID controllers • May be a discrete entity • DS4800, DS5000 • or integrated with disks • DS3000, DS4700 • What is a RAID controller? • Handles all I/O operations to the underlying media • Provides data protection via RAID configuration • Basic management interface as well as premium features • The type of Storage Server determines the product model (e.g. DS3200 or DS5300) Cache Cache memory controller with RPA Host interface Drive interface

  5. Expansion enclosures • Provides housing for individual disk drives • Connects to the controller via ESMs (environmental service modules) • Two major types of current expansion enclosures • SAS-based • EXP3000 for DS3000 products • FC-based • EXP810 / EXP5000 for DS4000 / DS5000 products

  6. Disks • DS4000 and DS5000 supports FC and SATA disks • May be intermixed within an expansion enclosure • DS3000 supports SAS and SATA disks • May be intermixed within an expansion enclosure

  7. FC? SAS? SATA? • FC and SAS drives are very similar in terms of performance and reliability • SATA have larger capacities and a better price per GB, however- • They are significantly ‘slower’ than either FC or SATA disks • The may have a lower designed duty cycle • For database or other I/O oriented applications, SATA drives are probably not a good fit • Slower rotational speed • Higher access time • Somewhat limited command queuing • Sequential large block read performance can be similar

  8. Logical components of a storage system • Arrays and logical drives • More commonly known as RAID sets and LUNs • An array is a group of disks which are grouped together using a distinct protection scheme • RAID 0, 1, 3, 5, 10, or 6* • Group size may be either 30 drives for RAID 3, 5, and 6 or system max. for RAID 0 and 10 • The host/server has no knowledge of the underlying RAID configuration • A logical drive is an element of the array • A given logical drive can be from 10MB to the entire size of the array it is contained in • You can have multiple logical drives per array • The logical drive is the entity that is mapped to a given server • To the server, the logical drive appears as a direct-attached SCSI disk of the size determined by the user • Logical drives on the same array may be mapped to different servers (and have very different properties) Array of 3 drives RAID 5, 2+P Logical drive 1 – x GB Logical drive 2 – x GB * RAID 6 is supported on the DS3200, DS3300, DS3400, DS4700, DS5100, and DS5300

  9. RAID = Redundant Array of Inexpensive Disks • Why use RAID? • Enhanced performance • Access to data (disks are mechanical device and will fail!) • An array must have an associated RAID level • For DS3/4/5000 products • RAID 0, 1, 3, 5, 10, 6 • RAID 0 – from a single drive to all of the drives in the system • RAID 1 – two drives • RAID 3 – from 3 drives to 30 drives • RAID 5 – from 3 drives to 30 drives • RAID 10 – from 4 drives to all of the drives in the system • RAID 6 – from 5 drives to 30 drives • Physical location of drive(s) is not relevant in the DS3/4/5000 products • Same type of drives must be in a given array (i.e. FC, SAS, SATA) • What’s the difference?

  10. RAID 0 • Simple striping • Not actually redundant • If a drive fails, there is no ability to recover the failed data • Due to lack of redundancy, very infrequently used • Temp. space • Useable capacity = raw capacity File A A1 A2 A3 A4 A5 Drive 1 Drive 2 Drive 3 Drive 4 Drive 5 RAID 0 Array

  11. RAID 1 • Simple mirroring • Only allows for 2 drives maximum • Due to lack of scalability, very infrequently used • Small write intensive items, like database log files • Useable capacity = ½ raw capacity File A A A’ Drive 1 Drive 2 RAID 1 Array

  12. RAID 10 • Mirroring and striping • For DS3/4/5000, a specialized subset of RAID 1 containing more than 2 drives • Must be even number of drives • Very common usage • Typically applications that have high amounts of write activity or perform high amounts of random I/Os • Useable capacity = ½ raw capacity File A A1 A1’ A2 A2’ Drive 1 Drive 2 Drive 3 Drive 4 RAID 10 Array

  13. What is parity? • RAID levels 3, 5, and 6 all use ‘parity’ to allow for redundancy of information • Parity generated at the hardware level (remember RPA?) using a mathematical XOR • XOR can be generically thought of as ‘either A or B, but not both’ • Consider the following (grossly simplified) example- 1 0 1 Block of data #1 (data A) Block of data #2 (data B) Block of data #3 (parity)

  14. RAID 3 • Striping with parity information • Generally used for streaming or sequential workloads • Parity is rotating • Due to similarity to RAID 5, RAID 5 is typically used instead • Useable capacity = (raw capacity – 1 disk for parity) File A A1 A2 A3 A4 Ap Drive 1 Drive 2 Drive 3 Drive 4 Drive 5 RAID 3 Array

  15. RAID 5 • Striping with parity information • Most widely used RAID type • Parity is rotating • Useable capacity = (raw capacity – 1 disk for parity) File A A1 A2 A3 A4 Ap Drive 1 Drive 2 Drive 3 Drive 4 Drive 5 RAID 5 Array

  16. RAID 6 • Striping with parity plus an add’l separately calculated protection element (q) • Generally used for environments with SATA drives • Can sustain 2 drive failures in the group • Parity and q value are rotating • Useable capacity = (raw capacity – 2 disks for parity information) File A A1 A2 A3 Ap Aq Drive 1 Drive 2 Drive 3 Drive 4 Drive 5 RAID 6 Array

  17. Summary Storage Server Drive enclosure Array Logical drive Drives

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