Reality Check: Server Insights : drives

2.5-inch Drives vs. 3.5-inch Drives

s_mathur — Tue, 28 Apr 2009 20:41:00 GMT

While the majority of the internal and external systems use 3.5-inch drives, HP has lead the path to 2.5-inch drives through its server and storage offerings. Some would argue that the lower cost per GB is the reason why the 3.5-inch drives have remained so popular; others would point to the capacity gap - 2.5-inch drives offer about half the capacity of 3.5-inch drives. However, there's a growing number of people who have realized the energy costs need to be considered as well as the acquisition cost per GB.

IDC discusses the capacity gap, the cost to power and cool storage, as well as the industry transition to 2.5-inch drives in a whitepaper available at: http://h18004.www1.hp.com/products/servers/proliantstorage/drives-enclosures/docs/216652_IDC_Paper_2009FEB20.pdf.

In the paper, IDC states:

The 2.5inch SFF performance-optimized HDD is already well-recognized for providing greater storage density and higher IOPS per U in server and storage systems as well as consuming less power. But a 2.5inch form factor HDD carries a capacity penalty of roughly half that of a similar-generation 3.5inch HDD. The reason is simple: 3.5inch HDDs can have a maximum of four platters per drive, while current performance optimized 2.5inch HDDs have a maximum of two platters per drive. However, this is not a fixed rule, and HDD configurations are about to change.

IDC goes on to predict that "the HDD industry's last generation of 3.5inch performance-optimized HDDs will be launched in 2009."

Do you agree that the server and storage industry will transition to 2.5-inch drives faster than before?

Solid State Develops

s_mathur — Fri, 24 Apr 2009 13:52:00 GMT

By Susan Riley. There seems to be a lot of interest in SSD's lately. With all the different product offerings out there it is hard for the user to fully understand what type of product they need. There is the MLC variety that is high performance, higher capacity but lower endurance based on the number of write cycles and then there is the more expensive, smaller capacity SLC offerings that delivers higher performance and higher endurance levels. What to choose? MLC is typically used in consumer applications while SLC has developed in the enterprise space. The suppliers range in experience from drive suppliers to memory suppliers to smaller start up companies that put components on a PCBA and sell it as solid state. We segment the solutions into 4 categories, those that are externally attached (highest latency), "drive like" solutions, those that install on the PCIe bus and those that fit on the memory bus (lowest latency).

Visit our website to learn more: www.hp.com/go/solidstate.

How fast are your hard drives?

s_mathur — Tue, 21 Apr 2009 03:54:00 GMT

When it comes to choosing hard drives, there are several measures of performance that may influence your decision.

An important parameter for overall drive performance is revolutions per minute (abbreviated rpm, RPM, r/min, or r·min⁻¹); this is the speed at which the disk platters spin. High rpms mean data passes the read/write heads of the drive faster. In general, the higher the rpm of the drive, the faster data is accessed or stored on the platter. Drive vendors normally state the rpms of a drive as part of the name. HP SATA drives currently spin at 5400 or 7200 rpm while HP SAS drives come in 7200, 10,000, or 15,000 rpm speeds.

IOPS (input/output operations per second) is a set of common benchmarks for hard disks measuring the number of:

Sequential read
Sequential write
Random read, or
Random write

I/O operations per second (or a combination of all four). IOPS is normally measured in laboratories and so real life performance can vary greatly depending on the nature of the application and the system architecture as a whole. Note that random IOPS figures depend on the drive’s random seek time, whereas the sequential IOPS numbers are an indicator of the data transfer rate of the drive.

Seek time is the time it takes to move the read/write head to the right place on the platter. Related to seek time is rotational delay or latency: the time required for the addressed area of the disk to rotate to the position where the read/write head can get to it. The transfer time is the time it takes to actually read or write data from/to the platter. All three of these and spin-up time (the time needed to speed the disk to operating speed )determine the disk access time of a drive.

One other common term used when talking about drive performance is data transfer rate. This is often measured in bits per second and refers to the average rate data is moved from the drive to the storage controller. Often when people talk about data transfer rate, they are actually talking about system bandwidth or throughput, which is the rate at which data travels from the drive to other components of the server/system. The throughput of the system depend on the data transfer rates of the drive, the controller, and the system BIOS and chipset – any one of these can be a bottleneck.

So, is rpm the most important measure of drive performance for your application/environment, or do you normally pay more attention to the other measures?

Are 6Gbps SAS drives right for your environment?

s_mathur — Mon, 13 Apr 2009 20:42:00 GMT

So, you’ve heard about the transition to 6Gb/s SAS drives and HP is at the front of this transition, like most others; but does your environment really need the greater system throughput, the improved zoning, enhanced diagnostics, multiplexing and spread spectrum clocking (SSC) – among other benefits of 6G SAS?

The experts agree the new SAS interface is technically more robust than current interface technologies. When it comes to system performance, the benefits of 6G SAS technology can be seen in applications which aggregate multiple components, resulting in higher bandwidth for the whole system. Storage-intensive, high I/O applications such as video streaming, backups, large databases, high online transactions, and virtualization will benefit from the higher throughput of storage and other system devices.

But keep in mind: if you are looking to achieve a 6Gb/s line rate, you need an end-to-end 6G infrastructure, including server backplanes, HBAs and storage controllers, as well as drives. If any of the components of a storage subsystem operate at different data transfer rates, the system bandwidth will be negotiated down to an acceptable level for all components. The good news is that you don’t have to upgrade your whole infrastructure at once. The new HP 6G SAS drives that launched on March 30 are backward (hmm…and sideways?) compatible with 6G/3G SAS and 3G/1.5G SATA drives.

So, the 6G SAS drives have advanced features, improve performance, and work with your current hardware. It sounds like your environment can benefit from 6G SAS drives.

6Gbps SAS drives for G6 servers

s_mathur — Wed, 08 Apr 2009 18:20:00 GMT

With double the data rate of traditional 3Gb/s SAS drives, the new 6Gb/s SAS drives bring you an opportunity to break through the system bottlenecks of the past. Ramping up to 6Gb/s means greater system bandwidth than before.

Speaking of data rate, let's quickly dispel the confusion between 'data rate' and 'RPM.' Data rate or line rate is the speed at which data travels from the disk to the HBA or storage controller; while RPM is the rotational speed of the drive platters (in rotations per minute). One more thing - data transfer speed is not influenced by access time or latency.

On March 30, HP introduced the 146/300GB 6G SAS 10K 2.5in DP ENT drives (the first two 6G SAS drives) to the portfolio. If you have HP DL360 G6, DL380 G5, or BL460c G6 servers in your environment, it's easy to take full advantage of these high-performing, dual port 6Gb/s SAS drives.

Note that for a storage subsystem to truly operate at 6Gb/s, the drive, the HBA or storage controller, and the server backplane must have 6Gb/s data transfer rates, or the system will negotiate down to an acceptable level for all components. Refer to teh server and HBA/controller technical specifications for transfer rate details.