; A Reference Guide for Optimizing Dell™ SCSI Solutions Authored By: Dell SCSI Storage Solution Team November 17, 2005 rev A02 ____________________ Information in this document is subject to change without notice. © Copyright 2005 Dell Inc. All rights reserved. Reproduction in any manner whatsoever without the written permission of Dell Inc. is strictly forbidden. THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 TABLE OF CONTENTS A REFERENCE GUIDE FOR OPTIMIZING DELL SCSI SOLUTIONS ............................................................... 3 1. 2. INTRODUCTION ................................................................................................................................................... 3 STORAGE APPLICATIONS AND COMPONENTS ....................................................................................................
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 A Reference Guide for Optimizing Dell SCSI Solutions 1. Introduction Enterprise storage applications involve interconnection of multiple components – including both software and hardware aspects which would complete a storage solution. Any given storage application may be supported by one or more storage solutions. Thus, it becomes essential to identify an optimum storage solution, one which would be ideal for a given application.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Understanding each of the storage components with respect to these attributes will help in making intelligent decisions to determine an optimal configuration for a given application. The paper presumes that the reader has a basic understanding of different levels of RAID and interconnects technologies – Parallel SCSI (SPI-4), PCI vs. PCI-X vs. PCI-e.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 the server/storage solution and will determine what RAID configuration will be the most optimal for the application. Table 2-2 outlines the recommended RAID solution based on the usage of the server.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 RAID 5 RAID 5 has good I/O performance, data protection and relative cost with excellent storage capacity. RAID 5 should be used in situations where maximum storage capacity is required along with a moderate amount of data protection. RAID 50 A balance between RAID 5 and RAID 10, this solution offers good I/O performance, availability and good storage capacity.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • RAID 10 – Recommended for enterprise mission critical e-mail servers where availability and redundancy and/or performance are the highest priority and reduce storage capacity is acceptable. • RAID 5 – Recommended for e-mail servers that require maximum storage capacity and only base data protection and performance.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • RAID 5 – Recommended for databases that require maximum storage capacity and only base data protection and performance. • RAID 50 – Recommended for those solutions that require a balance between storage capacity and performance. Possible: • RAID 1 – Possible solution for small databases which do not require high storage capacity.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • RAID 5 – Recommended for web servers that require maximum storage capacity and only base data protection and performance. • RAID 50 – Recommended for those solutions that require a balance between storage capacity and performance. • RAID 0 – Recommended for solutions where web server will be part of a group of web servers that service a large internet portal and performance is the highest concern.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS • VER A02 RAID 50 – Recommended for those solutions that require a balance between storage capacity and performance. Possible: • RAID 1 – Possible solution for situations which do not require high storage capacity. Not recommended: • RAID 0, Concatenated - These are not recommended due to lack of redundancy and data protection. Note: While these configurations are not recommended, they can be configured and utilized.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS • VER A02 RAID 1 – Possible solution in situations which do not require high storage capacity. Not recommended: • RAID 0, Concatenated - These are not recommended due to lack of redundancy and data protection. Since long term archival storage is indented in some ways to be a backup of important files, it is not a recommended solution. Note: While these configurations are not recommended, they can be configured and utilized.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 that can afford some downtime and rely on backups to restore data, this could be a solution. Streaming Media Servers Streaming media servers are systems that provide web casting, video conferencing, internet entertainment like TV or radio, and multimedia content oriented services. These are systems that generally require a balance between storage capacity, availability, redundancy and performance.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Additional configuration factors Hot Spares Hot Spare functionality provides extra security availability and redundancy by replacing a failed drive, allowing the rebuild of the degraded array to begin immediately. Both the Adaptec and LSI based PERC controllers’ support this feature, but a simple SCSI controller would not. See the controller user’s guide for details and limitations. Use of Hot Spares is recommended whenever possible.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 3. Dell’s Product Offering PowerVault™ 220S & 221S Storage Enclosure Dell™ PowerVault 220xS systems are flexible, external SCSI expansion enclosures designed to support multiple Dell storage environments and RAID configurations. Each system offers maximized drive-spindle count, hot-plug hard drives, optional redundant power, redundant cooling, rack mount capability, systems management features, and a modular design for easy upgrades.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 (SCSI) host adapter with RAID control capabilities. It provides reliable fault-tolerant disk subsystem management and is an ideal RAID solution for internal storage in Dell's PowerEdge enterprise systems. The RAID controller offers a cost-effective way to implement RAID in a server. Dell is currently offering its fourth generation of RAID controllers, the PERC 4e family, supporting the industry standard Ultra320 SCSI storage interconnect.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • Table 3-2: PERCs and Cable Type PV22xS Controller/Cable Matrix Controller type PERC Add-in Cards PERC 2/DC PERC 2/QC PERC 3/QC PERC 3/DCL PERC 3/Di Embedded PERC 4/DC PERC 4/Di Embedded PERC 4e/DC PERC 4e/Di Embedded SCSI HBAs Adaptec 3960D (39160) Cable type Wide HD to Slim VHDCI Wide HD to Slim VHDCI Wide HD to Slim VHDCI Wide HD to Slim VHDCI Wide HD to Wide HD on PE2600, PE2500, and 4400 Slim VHDCI to Wide HD on PE1650, PE1750 Wide H
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 In addition, many Dell servers & storage solutions offer cross generational support to ensure customers have a seamless experience when adopting new technologies.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • Table 3-4: PERC 2 & PERC 3 Support Matrix (4G & 5G servers) Y = Supported, N = Not Supported, # = maximum # of factory installed cards FI = Factory install; CK = Customer Kit 2/SC 2/DC 3/DI System 3/SC FI CK 3/DCL FI CK FI 3/DC CK FI 3/QC CK PowerEdge Server Support PE 500SC PE 600SC PE 1400 PE 1400SC PE 1500 PE 1550 PE 1600SC PE 1650 PE 2400 PE 2450 PE2500 PE 2550 PE 2600 PE 2650 PE 3250 PE 7250 PE 4400 PE 4600 PE 6400 PE 6450 PE 660
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 4. PV22xS Enclosure Overview The PV22xS SCSI Enclosure provides three configuration topologies, also referred to as modes, which are end-user configurable: Joined, Split, and Cluster topologies, as shown in Figure 4-1. A 3-position switch located on the Split Bus Module (SBM) sets the desired enclosure topology. Each of these topologies will be further explained in more detail below.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 The primary EMM must always be present. Regardless of whether SES redundancy is available, the secondary EMM slot must always have either a EMM or Terminator module installed to properly terminate the SCSI bus. Leaving this slot unpopulated is not supported and will have undesirable consequences. Configurations with two EMMs and one cable connected provide a level of redundancy.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Figure 4-3 Split Bus Cabling Options to a Single Host System, (a) Same Adapter, (b) Different Adapters Cluster Topology Cluster Topology is very similar to Joined bus topology. It provides the capability to have a single shared SCSI bus with the additional capability of allowing concurrent access from two host controllers (Figure 4-4).
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 a failover condition, access rights to the disk array assigned to the failed node is transferred to the other node. An active/active cluster node must be sized appropriately to handle the load of both nodes (in the event of a failover).
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 be reserved for use by the second SCSI controller. A mapping of the SCSI ID address space reserved by the PV22xS enclosure is shown in Figure 4-5. The HDD identifiers are directly mapped to it’s assigned SCSI ID, as shown in Figure 4-6. Figure 4-5 SCSI ID Assignments Figure 4-6 SCSI ID Numbers and Associated Hard Disk Drives Multiple PV22xS Enclosures on a Single Host System Daisy chaining of Multiple PV22xS enclosures is not supported.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 modules is not supported. For more details, refer to section 5 (SCSI Host Bus Adapters / SCSI RAID). Actual transfer rate of the SCSI bus is determined by host channel, EMMs and HDDs installed in PV22xS. Mixing HDD Capacities Mixing of different drive sizes is supported, but not recommended. PV22xS currently supports 18GB, 36GB, 73GB, 146GB, and 300GB capacities, with future support for higher capacities as they become available.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 properly quiescent before the remove/replacement operation takes place, whereas hot plugging can occur at any time without prior notification. Hot plugging allows the user applications and disk activities to continue uninterrupted while maintenance or repair actions are taking place. Warm plugging requires synchronization with the software applications to temporarily halt disk I/O activity before the hardware is removed/replaced.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Cable Connector Controller Connector P-type connector – Male P-type connector – Female VHDCI-type connector – Male VHDCI-type connector – Female • Figure 4-7 External SCSI Connector PV22xS Configuration Topology and Application Attributes PV22xS provides different configuration topologies, which may impact the storage solution for an application.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • Table 4-2: PV22xS Configuration Topologies Vs RAID Level Performance PV22xS Configuration Topologies RAID Levels Joined RAID 0 Default RAID 0 performance RAID 1 Default RAID 5 Default RAID 10 Default RAID 50 Default Split Best performance, if configured across multiple channels Increased Availability, if mirror set is on separate channel Default Higher performance than RAID 1 with same increased availability Increase availability,
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 PV22xS consists of four digital temperature probes, which in conjunction with SES processor provides device protection against adverse thermal conditions. PV22xS is designed to operate at ambient temperature of 10OC to 35OC. Once the temperature probe detects ambient temperature to be below 0OC or above 50OC, SES processor notifies host of critical temperature range, which would then initiate a thermal shut down process.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 5. SCSI Host Bus Adapters / SCSI RAID This section addresses concerns specific to RAID. A summarized table (Table 5-2) is presented at the end of the section which provides an overview of the Dell SCSI and RAID solutions that support PV22xS. Although attachment of PV22xS to 39160 SCSI HBA is supported, it is not recommended.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Controller Family Aside from the technical, physical and feature differences between the controller families (see Table 5-2), there are a few critical differences which impact behavior of these controllers and hence a storage solution. Dell’s Storage controllers can be broadly categorized into two families – Adaptec PERCs and LSI PERCs.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 In contrast, Adaptec controllers will only use space on all ‘child’ arrays equal to the available space on the smallest ‘child’ array, and will leave the remaining space on the larger drives unused and available, and the performance behavior will not be affected as the array fills up.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 back up unit (see Table 5-2), there is a risk of data loss if system power is lost while unwritten information is still in the cache. o Write Through In write-through caching, a data transfer is completed when the disk subsystem receives all of the data from the host.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 For more details on rebuild process please refer to Appendix A – Reference 5: Maintenance Best Practices for Direct Attached SCSI Solutions • Patrol Read o Patrol Read is a preventative maintenance background operation (available only on PERC 3 (except PERC 3/DI), PERC 4 and PERC 4e controller families running 3.0 and higher firmware).
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 drives supported by the PV22xS). Mixing spindle speeds within the same array will impact array performance, especially in a striped (RAID0, RAID10 or RAID50) environment. Higher RPM drives will have to wait for the slower ones to complete the operations. This is the case regardless of cache policy settings.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • Table 5-1: Pros and Cons for Spanning Arrays with various RAID Levels Level Pros RAID 0 Improves data throughput by optimizing bandwidth utilization RAID 1 Improves data availability against channel failures, if mirrored set is spanned across separate channel RAID 5 May improve data throughput for certain accesses, if data and parity for the access span across channels RAID 10 Improves data availability against channel failures, if
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Table 5-2 – Controller Families & Features: Part 1 PERC 4/Di (PE1750) PERC 4e/DC Wide Ultra320 x4 PCI Express (Embedded) Wide Ultra320 X8 PCI Express (HBA) Wide Ultra320 # Channels 2 2 2 # internal connectors 2 x 68-pin HD 2 x 68-pin HD 2 x 68-pin HD # External Connectors 1 x 68-pin UHD 2 x 68-pin UHD 1 x 68-pin HD n/a (hardwired to backplane) 1 x 68-pin UHD 0, 1, 5, 10, 50 0, 1, 5, 10, 50 0, 1, 5, 10, 50 0, 1, 5, 10, 50
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Table 5-2 – Controller Families and Features: Part 2 PERC 4/SC PERC 4/DC SCSI Technology Wide Ultra320 Wide Ultra320 Wide Ultra3 / U160 Wide Ultra3 / U160 Host Bus Interface 64-bit / 66 MHz PCI 2.2 (HBA) 64-bit / 66 MHz PCI 2.2 (HBA) 64-bit / 66 MHz PCI 2.2 (HBA) 64-bit / 66 MHz PCI 2.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 Table 5-2 – Controller Families and Features: Part 3 PERC 3/DC PERC 3/QC PERC 3/Di PERC 2/QC SCSI Technology Wide Ultra3 / U160 Wide Ultra3 / U160 Wide Ultra3 / U160 Wide Ultra 2 Host Bus Interface 64-bit / 66 MHz PCI 2.2 (HBA) 64-bit / 66 MHz PCI 2.2 (HBA) 64-bit / 66 MHz PCI 2.2 (Embedded) 64-bit / 33 MHz PCI 2.1 (HBA) Adaptec 39160 Wide Ultra3 / U160 64-bit / 66 MHz PCI 2.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 6. Summary and Conclusions After analyzing and assessing the importance of all the storage components relative to attributes essential for performance of any given application, it can be observed that not only understanding the characteristics of each storage component is critical but also how the storage component is configured has direct impact on the effectiveness of an application.
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 • Table 6-1: Typical Storage Recommendation for Different Storage Applications Application Servers Key Parameters Storage Recommendations RAID Level PV22xS Host Controller For added performance enable Write back cache, if available on PERC If added performance is required enable Write back cache, if available on PERC Email * Availability * Performance * Scalability RAID10 Provides both Availability and performance Cluster Topology Scal
A REFERENCE GUIDE FOR OPTIMIZING DELL™ SCSI SOLUTIONS VER A02 7. Appendix – A: References 1. ANSI T10/1365D SCSI Parallel Interface – 4 (SPI-4) and SCSI Block Commands – 2 (SBC-2) (http://www.t10.org) 2. Dell™ PowerVault™ 220S and 221S Systems Documents (http://support.dell.com/support/edocs/stor-sys/spv22xs/en/index.htm) 3. Dell ‘Getting Started with RAID’ document (http://support.dell.com/support/edocs/storage/RAID/RAIDbk0.pdf) 4. Dell High Availability Cluster (http://www1.us.dell.
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