General |
| Q1. |
What is a Serial Attached SCSI (SAS)? |
| A1. |
Serial Attached SCSI (SAS) is the evolution of the SCSI interface. 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.
SAS Enterprise drives satisfy the enterprise data center requirement of scalability, performance, reliability and manageability, while providing an enterprise storage infrastructure for both enterprise SAS drives and SATA disk drives. SAS Midline drives provide the lowest dollars per gigabyte and economical reliability and performance. The SAS interface is compatible with SATA devices. This compatibility provides users with unprecedented choices for server and storage subsystem deployment.
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| Q2. |
How does Serial Attached SCSI (SAS) benefit the storage industry? |
| A2. |
SAS leverages the proven SCSI interface 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 parallel SCSI environments. SAS's compatibility with SATA devices will provide customers a downstream compatibility with desktop class ATA technologies.
Simplified signal routing and smaller connectors enable dense devices, such as small form factor hard drives, enabling storage solutions to better scale externally.
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| Q3. |
What are the end user benefits of Serial Attached SCSI (SAS)? |
| A3. |
Key end user benefits of SAS Enterprise drives 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, 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. SAS Midline drives provide the customer with a high-capacity, economical solution for server or external storage environments where economical reliability and performance are required.
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| Q4. |
What capacities are available, and what are their part numbers? |
| A4. |
See the SAS Enterprise and SAS Midline Quickspecs at http://h18004.www1.hp.com/products/quickspecs/12244_div/12244_div.html for a current list of HP SAS drives. |
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Technical |
| Q1. |
What is the speed of the SAS drives? |
| A1. |
The 2.5-inch SAS Enterprise drives spin at 10,000 & 15,000 RPMs and the 3.5-inch at 15,000 RPMs. The 3.5-inch SAS Midline drives spin at 7200 RPMs. HP SAS drives have 3Gb/s
or 6Gb/s interface speeds. |
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| Q2. |
What are the power and cooling benefits of the 2.5" SAS Enterprise drives? |
| A2. |
SFF SAS Enterprise drives consume 70% less space and use about 50% less power than the 3.5" drives. The smaller form factor of the drives allows systems to be designed to accommodate more drives per U increasing the total system IOPs/U. Smaller disk drives and tighter packing also improve system and cabinet airflow, helping reduce cooling costs and enabling greener, more energy efficient systems |
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| Q3. |
Does SAS support dual ported drives? |
| A3. |
Yes, the SAS specification does include support for dual ported drives. SATA drives will remain single ported.
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| Q4. |
Are dual port drives compatible with single port servers and enclosures? |
| A4. |
Yes, dual port SAS drives are compatible with servers and storage enclosure which only support one port on the hard drive. The drive will function as a single port device in this configuration. |
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| Q5. |
When should a customer use dual ported hard drives? |
| A5. |
Dual port SAS drives are the standard in the drive industry and single port drives are being phased out. Dual port hard drives are ideally suited for dual port enabled external storage systems requiring high levels of redundancy and dual data paths to the hard drive. Dual port SAS drives may also be deployed in single port servers and enclosures where the highest levels of reliability and performance are a requirement. |
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Other |
| Q1. |
Is Serial Attached SCSI (SAS) complementary to Serial ATA (SATA)? |
| A1. |
SAS complements SATA by adding dual porting, full duplex, device addressing and it offers higher reliability, performance and data availability services, as well as logical SCSI compatibility. It will continue to enhance these metrics as the specification evolves, including increased device support. SATA is targeted to cost-sensitive low work load non-mission-critical storage environments. Most importantly, these are complementary technologies based on a universal interconnect, where SAS customers can choose to deploy cost-effective SATA drives in a SAS storage environment. |
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| Q2. |
Are SAS connectors compatible with those of SCSI server and storage solutions? |
| A2. |
No, SAS connectors differ from current SCSI connectors. |
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| Q3. |
When should a customer use SAS HDDs? |
| A3. |
Customers should use SAS Enterprise drives in servers and storage solutions with mission critical and high work load intensive applications where near 24/7 duty cycles are a requirement, such as database applications and high transaction level applications. SAS Midline drives should be used when the customer requires high-capacities, moderately-priced reliability and performance for non mission-critical, low workload applications, such as disk backup, archival, and reference applications.
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| Q4. |
Could I mix SAS and SATA drives the same server or storage system? |
| A4. |
Yes, SAS allows the flexibility to install SAS drives, SATA drives or a mix of both SAS and SATA drives in the same enclosure, so long as the system is an inherent SAS system. Mixing of SAS and SATA drives in the same logical volume is not supported. |
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| Q5. |
Where can I find the SAS compatibility information? |
| A5. |
The SAS compatibility charts can be found on the HP ProLiant Server Compatibility Guide.
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Service Warranty |
| Q1. |
What is the warranty period for a SAS drive? |
| A1. |
SAS Enterprise drives offer a three year warranty. SAS Midline drives offer a one year warranty similar to other HP Midline drives. |
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Performance |
| Q1. |
What is the rotational speed of a drive? |
| A1. |
This is the speed at which the drive platters spin, usually measured in rotations per minute (RPM). SAS Enterprise drives spin at two different speeds: 10K or 15K RPM; while SAS Midline drives spin at 7.2K RPM.
While the actual application can make a difference, in general, the faster the platters spin, the faster data is accessed from the disk platter.
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| Q2. |
What is the data transfer rate? |
| A2. |
For drives, transfer rate is the speed at which data can be moved between the drive and controller. SAS drives have transfer rates of 3Gb/s and 6Gb/s. Note: transfer speed is not influenced by rotational speed, access time or latency |
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| Q3. |
What kinds of environment are ideal for 6Gb/s SAS drives? |
| A3. |
Although HP 6Gb/s SAS drives will work in any enterprise environment, they are ideal for those storage-intensive environments where a large number of drives are used. Because 6Gb/s SAS gives more system bandwidth, the performance of more drives can be aggregated before saturation. Some examples of I/O-intensive environments that could benefit from a 6Gb/s SAS
infraestrucure are virtualization environments, video streaming and hot backups (where performance is critical). |
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