| General |
| Q1. |
What is Serial Attached SCSI? |
| A1. |
Serial Attached SCSI (SAS) is the logical evolution that satisfies the enterprise data center requirement of scalability, performance, reliability and manageability, while leveraging a common electrical and physical connection interface with Serial ATA (SATA). This compatibility provides users with unprecedented choices for server and storage subsystem deployment. |
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| Q2. |
Why was SAS developed? |
| A2. |
SAS was developed to address anticipated I/O and direct attach storage requirements in the future. It provides universal interconnect with SATA, while offering logical SCSI compatibility along with SCSI reliability, performance and manageability. |
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| Q3. |
What are the end user benefits of Serial Attached SCSI? |
| A3. |
Key end user benefits include enterprise class robustness, investment protection in compatible SCSI software and middleware and the choice of direct-attach storage devices (SAS or SATA). In addition, greater performance, longer cabling distances, smaller form factors and greater addressability will all lead to a new level of flexibility when deploying mainstream data center servers and subsystems. Since SAS is based on the foundation of the industry-leading SCSI specification, reliability and peace of mind will satisfy user's needs for continuity in the data center. |
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| Q4. |
How does Serial Attached SCSI benefit the storage industry? |
| A4. |
SAS leverages the proven SCSI technologies that customers expect in data center environments, providing robust solutions and generational consistency. It is based on a serial interface, allowing for increased device support and bandwidth scalability, and reducing the overhead impact that challenges today's SCSI environments. It utilizes SATA development work on smaller cable connectors, providing customers a downstream compatibility with desktop class ATA technologies.
Simplified routing will enable a new generation of dense devices, such as small form factor hard drives, enabling storage solutions to scale externally. |
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| Technical questions - cache/memory |
| Q1. |
Is Drive Write Cache available on HP SATA drives? |
| A1. |
Yes, however HP ships SATA drives with Drive Write Cache (DWC) disabled. The preset configuration was selected to provide greater safety for our customer's drive data in case of sudden power loss, when there is no battery on the controller to protect the cache.
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| Q2. |
Can Drive Write Cache be enabled on the controller and SATA drives? |
| A2. |
Yes, please see the attached presentation for the latest servers and controllers that allow for Drive Write Cache to be enabled.
WARNING: Enabling DWC may result in loss of data if power is lost to the server and there is no power protection configured for the server. When Drive Write Cache is configured, the following best practices should be used to protect the data in case of power loss: Install a redundant power supply in the server (if available for that server). If redundant power supplies are used and one power supply fails, temporarily disable Drive Write Cache until a replacement power supply has been installed. If redundant power supplies are used, add an additional layer of power protection by connecting each power supply in the server to a separate Uninterruptible Power Supply (UPS). If multiple UPSs are used, add an additional layer of power protection by connecting each UPS to a different AC circuit.
How to Enable Write Cache on SATA HDDs for HP ProLiant ML100 series and ML310DL320 Servers DWC
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