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Storage Area Network Usage A UNIX SysAdmins View of How A SAN Works.

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Presentation on theme: "Storage Area Network Usage A UNIX SysAdmins View of How A SAN Works."— Presentation transcript:

1 Storage Area Network Usage A UNIX SysAdmins View of How A SAN Works

2 Disk Storage Embedded Internal Disks within the System Chassis Directly Attached External Chassis of Disks connected to a Server via a Cable Directly Attached Shared External Chassis connected to more than one Server via a Cable Networked Storage NAS SAN others

3 Disk Storage – TypeBus SpeedDistanceCable Pins ATA100 MB/s18 inches40 SCSI320 MB/s12 m68 or 80 FC400MB/s10K m4 SATA-II300MB/s6 m22 SAS300MB/s10 m22

4 Deficiencies of Direct Connect Storage Single System Bears Entire Cost of Storage Small Server in an EMC Shop Large Server cannot easily share its unused storage Managability Fragmented and Isolated Scalability Limited What happens when you run out of peripheral bus slots? Availability SCSI Bus Reset Failover is a complicated add-on, if available at all

5 DASD Direct Access Storage Device They still call it this in an IBM Mainframe Shop Basic Limits of Disk Storage Recognized Latency Rotation Speed of the disk Seek Time Radial Movement of the Read/Write Heads Buffer Sizes Stop sending me data, I cant write fast enough!

6 SCSI SCSI – Small Computer System Interface From Shugarts 1979 SASI implementation SASI: Shugart Associates System Interface Both Hardware and I/O Protocol Standards Both have evolved over time Hardware is source of most limitations I/O Protocol has long-term potential

7 SCSI - Pro Device Independence Mix and match device types on the bus Disk, Tape, Scanners, etc… Overlapping I/O Capability Multiple read & write commands can be outstanding simultaneously Ubiquitous

8 SCSI - Con Distance vs. Speed Double the Signaling Rate Speed: 40, 80, 160, 320 MBps Halve the Cable Length Limits Device Count: 16 Maximum Low voltage Differential Ultra3 SCSI can support only 16 devices on a 12 meter cable at 160 MBps Server Access to Data Resources Hardware changes are disruptive

9 SCSI – Overcoming the Con New Hardware & Signaling Platforms SCSI-3 Introduces Serial SCSI Support Fibre Channel Serial Storage Architecture (SSA) Primarily an IBM implementation FireWire (IEEE 1394 – Apple fixes SCSI) Attractive in consumer market Retains SCSI I/O Protocol

10 Scaling SCSI Devices Increase Controller Count within Server Increasing Burden To CPU Device Overhead Bus Controllers can be saturated You can run out of slots Many Queues, Many Devices Queuing Theory 101 (check-out line) - undesirable

11 Scaling SCSI Devices Use Dedicated External Device Controller Hides Individual Devices Provide One Large Virtual Resource Offloads Device Overhead One Queue, Many Devices - good Cost and Benefit Still borne by one system

12 RAID Redundant Array of Inexpensive Disks Combine multiple disks into a single virtual device How this is implemented determines different strengths Storage Capacity Speed Fast Read or Fast Write Resilience in the face of device failure

13 RAID Functions Striping Write consecutive logical byte/blocks on consecutive physical disks Mirroring Write the same block on two or more physical disks Parity Calculation Given N disks, N-1 consecutive blocks are data blocks, Nth block is for parity When any of the N-1 data blocks are altered, N-2 XOR calculations are performed on these N-1 blocks The Data Block(s) and Parity Block are written Destroy one of these N blocks, and that block can be reconstructed using N-2 XOR calculations on the remaining N-1 blocks Destroy two or more blocks – reconstruction is not possible

14 RAID Function – Pro & Con Striping Pro:Increases Spindle Count for Increased Thruput Con:Does not provide redundancy Mirroring Pro:Provides Redundancy without Parity Calculation Con:Requires at least 100% disk resource overhead Parity Calculation Pro:Cuts Disk Resource Overhead to 1/N Con:Parity calculation is expensive N-2 calculations are required If all N-1 data blocks are not in cache, they must be read

15 RAID Types RAID 0 Stripe with No Parity RAID 1 Mirror two or more disks RAID 0+1 Stripe on Inside, Mirror on Outside RAID 1+0 Mirrors on Inside, Stripe on Outside RAID 3 Synchronous, Subdivided Block Access; Dedicated Parity Drive RAID 4 Independent, Whole Block Access; Dedicated Parity Drive RAID 5 Like RAID 4, but Parity striped across multiple drives



18 RAID 1+0RAID 0+1

19 Breaking the Direct Connection Now you have high performance RAID The storage bottleneck has been reduced Youve invested $$$ to do it How do you extend this advantage to N servers without spending N x $$$? How about using existing networks?

20 How to Provide Data Over IP NFS (or CIFS) over a TCP/IP Network This is Network Attached Storage (NAS) Overcomes some distance problems Full Filesystem Semantics are Lacking …such as file locking Speed and Latency are problems Security and Integrity are problems as well IP encapsulation of I/O Protocols Not yet established in the marketplace Current speed & security issues

21 NAS and SAN NAS – Network Attached Storage File-oriented access Multiple Clients, Shared Access to Data SAN – Storage Area Network Block-oriented access Single Server, Exclusive Access to Data

22 NAS: Network Attached Storage File Objects and Filesystems OS Dependent OS Access & Authentication Possible Multiple Writers Require locking protocols Network Protocol: i.e., IP Front-end Network

23 SAN: Storage Area Network Block Oriented Access To Data Device-like Object is presented Unique Writer I/O Protocol: SCSI, HIPPI, IPI Back-end Network


25 A Storage Area Network Storage StorageWorks MA8000 (24), EVA (2) HDS is 2 nd Approved Storage Vendor 9980 Enterprise Storage Array – EMC class storage Switches Brocade (8), 3800 (20), & 2800 (34) 3900s are being deployed – 32 port UNIX Servers on the SAN Solaris (56), IRIX (5), HP-UX (5), Tru64 (1) Storage Volume Connected to UNIX Servers GB as of May, 2003 Windows Servers Windows 2000 (74), NT 4.0 (16)

26 SAN Implementations FibreChannel FC Signalling Carrying SCSI Commands & Data Non-Ethernet Network Infrastructure iSCSI SCSI Encapsulated By IP Ethernet Infrastructure FCIP – FibreChannel over IP FibreChannel Encapsulated by IP Extending FibreChannel over WAN Distances Future Bridge between Ethernet & FibreChannel iFCP - another gateway implementation

27 NAS & SAN in the Data Center

28 FCIP In The Data Center

29 FibreChannel How SCSI Limitations are Addressed Speed Distance Device Count Access

30 FibreChannel – Speed 266 Mbps – ten years ago 1063 Mbps – common in Mbps – available today 4 Gbps – near future products Backward compatible to 1 & 2 Gbps 10 Gbps – 2005? Not backward Compatible with 1/2/4Gbps But 10 Gig Ethernet will compete Remember FDDI & ATM

31 Why I/O Protocols are Coming to IP IP Networking is ubiquitous Gigabit ethernet is here 10Gbps ethernet is just becoming available Dont have to invest in a second network Just upgrade the one you have IP & Ethernet software is well understood Existing talent pool for vendors to leverage Developers, not end-user Network Engineers

32 FibreChannel – Distance 1063 Mbps 175m (62.5 um– multi-mode) 500m (50.0 um– multi-mode) 10 km (9 um– single-mode) 2125 Mbps 500m (50.0 um– multi-mode) 2 km (9 um– single-mode)

33 FibreChannel – A Network Layer 1 – Physical (Media: fiber, copper) Fibre: 62.5, 50.0, & 9.0 um Copper: Cat6, Twinax, Coax, other Layer 2 – Data Link (Network Interface & MAC) WWPN: World Wide Port Name WWNN: World Wide Node Name In a single port node, usually WWPN = WWNN 64-bit device address Comparable to 48-bit Ethernet device addresses Layer 3 – Network (IP & SCSI) 24-bit fabric address Comparable to an IP address

34 FibreChannel Terminology: Port Types N_Port Node port – Computer, Disk, or Storage Node F_Port Fabric port – Found only on a Switch E_Port Expansion Port – Switch to Switch port NL_Port Node port with Arbitrated Loop Capabilities FL_Port Fabric port with Arbitrated Loop Capabilities G_Port Generic Switch Port: Can act as any of F_Port, E_Port, or FL_Port


36 FibreChannel - Topology Point-to-Point Arbitrated Loop Fabric

37 FibreChannel – Point-to-point Direct Connection of Server and Storage Node Two N_Ports and One Link

38 FibreChannel - Arbitrated Loop Up to 126 Devices in a Loop via NL_Ports Token-access, Polled Environment (like FDDI) Wait For Access Increases with Device Count

39 FibreChannel - Fabric Arbitrary Topology Requires At Least One Switch Up to 15 million ports can be concurrently logged in with the 24-bit address ID. Dedicated Circuits between Servers & Storage via Switches Interoperability Issues Increase With Scale

40 FibreChannel – Device Count 126 devices in Arbitrated Loop 15 Million in a fabric (24-bit addresses) Bit 0-7:Port or Arbitrated Loop addr Bit 8-15:Area, identifies FL_Port Bit 16-23:Domain, address of switch 239 of 256 address available 256 x 256 x 239 = 15,663,104

41 FibreChannel Definitions WWPN Zone & Zoning LUN LUN Masking

42 FibreChannel - WWPN World-Wide Port Number A unique 64-bit hardware address for each FibreChannel Device Analogous to a 48-bit ethernet hardware address WWNN - World-Wide Node Number

43 FibreChannel – Zone & Zoning Switch-Based Access Control Analogous to an Ethernet Broadcast Domain Soft Zone Zoning based on WWPN of Nodes Connected Preferred Hard Zone Zoning Based on Port Number on Switch to which the Nodes are Connected

44 FibreChannel - LUN Logical Unit Storage Node Allocates Storage and Assigns a LUN Appears to the server as a unique device (disk)

45 FibreChannel – LUN Masking Storage Node Based Access Control List (ACL) LUNs and Visible Server Connections (WWPN) are allowed to see each other thru the ACL. LUNs are Masked from Servers not in the ACL

46 LUN Security Host Software HBA-based firmware or driver configuration Zoning LUN Masking

47 LUN Security Host-based & HBA Both these methods rely on correct security implemented at the edges Most difficult to manage due to large numbers and types of servers Storage Managers may not be Server Managers Dont trust the consumer to manage resources Trusting the fox to guard the hen house

48 LUN Security Zoning An access control list Establishes a conduit A circuit will be constructed thru this Allows only selected Servers see a Storage Node Lessons learned Implement in parallel with LUN Masking Segregate OS types into different Zones Always Promptly Remove Entries For Retired Servers

49 LUN Security LUN Masking The Storage Nodes Access Control List Sees the Servers WWPN Masks all LUNs not allocated to that server Allows the Server to see only its assigned LUNs Implement in parallel with Fabric Zoning

50 LUN - Persistent Binding Persistent Binding of LUNs to Server Device IDs Permanently assign a System SCSI ID to a LUN. Ensures the Device ID Remains Consistent Across Reconfiguration Reboots Different HBAs use different binding methods & syntax Tape Drive Device Changes have been a repeated source of NetBackup Media Server Failure

51 SAN Performance Storage Configuration Fabric Configuration Server Configuration

52 SAN - Storage Configuration More Spindles are Better Faster Disks are Better RAID 1+0 vs. RAID 5 RAID 5 performs poorly compared to RAID 0+1 when both are implemented with software RAID Allan Packer, Sun Microsystems, 2002 Where does RAID 5 underperform RAID 1+0? Random Write Limit Partition Numbers Within RAIDsets

53 SAN - Fabric Configuration Common Switch for Server & Storage Multiple hops reduce performance Increases Reliability Large Port-count switches 32 ports or more 16 port switches create larger fabrics simply to carry its own overhead

54 SAN - Server Configuration Choose The Highest Performance HBA Available PCI: 64-bit is better than 32-bit PCI: 66 MHz is better than 33 MHz Place in the Highest Performance Slot Choose the widest, fastest slot in the system Choose an Underutilized Controller Size LUNs by RAIDset disk size BAD: LUN sizes smaller than underlying disk size

55 SAN Resilience At Least Two Fabrics Dual Path Server Connections Each Server N_Port is Connected to a Different Fabric Circuit Failover upon Switch Failure Automatic Traffic Rerouting Hot-Plugable Disks & Power Supplies

56 SAN Resilience – Dual Path Multiple FibreChannel Ports within Server Active/Passive Links Most GPRD SAN disruptions have affected single-attached servers

57 SAN – Good Housekeeping Stay Current With OS Drivers & HBA Firmware Before You Buy a Servers HBA Is it supported by the switch & storage vendors? Coordinate Firmware Upgrades Storage & Other Server Admin Teams Using SAN Monitor Disk I/O Statistics Be Proactive; Identify and Eliminate I/O Problems

58 SAN Backups – Why We Should Why We Should Offload Front-end IP Network Most Servers are still connected to 100baseT IP 1 or 2 Gbps FC Links Increase Thruput Shrink Backup Times Why We Dont Cost NetBackup Media Server License: starts at $5K list

59 Backup Futures Incremental Backups No longer stored on tape Use near-line cheap disk arrays Several vendors are under current evaluation Still over IP 1 Gbps ethernet is commonly available on new servers 10 Gbps ethernet needed in core

60 Questions

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