Increase transfer size, Analyze your I/Os

available in the file Stripe.txt on the CD which has been included with your ATTO ExpressPCI adapters.

Increase transfer size

If you are writing to an application that uses a lot of sequential disk I/O to a contiguous area on disk, you should use as large a transfer size as possible to reduce overhead on the system, on the SCSI bus and within disk drives.

Analyze your I/Os

For large sequential data transfers, use Direct I/O by selecting FILE_FLAG_WRITE_THROUGH and FILE_FLAG_NO_BUFFERING flags with your CreateFile call to avoid the overhead of copying data from one area of memory to another, to reduce the number of SCSI commands which must be executed and to leave system pages available for other data.

If your application requires a small number of I/Os and the transfers are rather small, however, you may get better performance by letting the system cache your data in the system pages.

You might want to use over-lapped I/O using the FILE_FLAG_OVERLAPPED option with the CreateFile call. Overlapped I/O allows the

application to send many commands to the device at once.

The ATTO Disk Benchmark program, included with the ExpressPCI Utilities on the CD shipped with your ExpressPCI adapter, shows the effect of using the above I/O modes.

❖If you turn off Direct I/O and set the file size to a value significantly less than the amount of memory in your computer, you will get some artificially high transfer rates because very little I/O is actually being performed by the SCSI device: all the activity is involved in transferring data between the application and the system pages.

❖As you increase the file size to a value more than the amount of memory in your computer, you will see marked performance degradation.

❖If you turn on Direct I/O, you can see the effect of removing the system pages from the overhead picture.

❖If you use overlapped I/O, you will see performance improvements in the low to medium transfer sizes.

❖However, depending on the amount of memory in your computer, you may not be able to use queue depths greater than 4 or 5.

Maximize performance

ATTO ExpressPCI Ultra/WIDE SCSI Host Adapters Express PCI PSC: Single-Channel Single-Ended Ultra/WIDE ExpressPCI DC: Dual-Channel Single-Ended Ultra/WIDE specifications

ATTO Technology is a leading provider of cutting-edge storage connectivity solutions, and their line of ATTO ExpressPCI Ultra/WIDE SCSI Host Adapters has showcased the company’s commitment to performance and reliability for demanding data applications. Specifically, the ExpressPCI PSC (Single-Channel Single-Ended Ultra/WIDE) and the ExpressPCI DC (Dual-Channel Single-Ended Ultra/WIDE) models cater to different user needs while maintaining industry standards.

The ATTO ExpressPCI PSC is designed for environments where a single channel is sufficient to meet the connectivity demands. This single-ended adapter supports Ultra/WIDE SCSI technology, enabling data transfer rates of up to 40 MB/s. The PSC is perfect for users who require efficient storage solutions without the complexity of handling multiple channels. With its robust design, this adapter excels in various applications, from small business servers to high-performance workstations, offering reliability in demanding environments.

On the other hand, the ATTO ExpressPCI DC doubles the capability with its dual-channel architecture. This feature allows for two independent SCSI buses, effectively doubling the potential data throughput. By utilizing ultra/WIDE SCSI technology, the DC can achieve a combined throughput of 80 MB/s, making it an optimal choice for users needing higher performance for tasks such as video editing, data intensive applications, and backups. The dual-channel configuration provides advantages in multitasking, enabling the simultaneous operation of multiple drives or devices.

Both models incorporate advanced technologies such as automatic bus termination and active negation, ensuring optimal signal integrity and reliability. Additionally, ATTO’s exclusive Advanced Data Flow Management technology enhances performance by intelligently managing data transfer to optimize bandwidth utilization, which is key in environments where data transfer speed and reliability are crucial.

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