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Performance

In the performance data that are shown below, three useful measurements are described:  (a) SCSI Bandwidth Performance, (b) iSCSI Bandwidth Performance, and (c) SCSI Virtual Tape Performance.  Each measurement includes a description of the Initiator machine and the Target machine, along with the software that is running on both.  In the case of the Bandwidth Performance measurements, Intel's IoMeter is used, and the IoMeter parameters are listed as well.

Performance can be a tricky thing to measure, and results can vary widely depending on the characteristics of the entire system when viewed as a whole (i.e. the computers that are used, the adapters, the PCI architecture, the devices, the software, the way the software is configured, etc.).  There are many variables, and changing even one of them can lead to very different results.  And on top of that, there are many different performance metrics that could potentially be cited.

But for this exercise, the objective is to keep it simple and demonstrate that reading from and writing to a disk-based VTAng backup appliance is much faster than reading from and writing to a regular tape device.  And in fact, the data support that conclusion, with D2D sustained transfer rates clocking in at least 2 to 3 times faster than native tape transfer rates.  This means that customers can expect to cut their backup and restore times at least in half (depending on what they're comparing it to), and they may do even better than that under certain circumstances.

One of the keys to achieving great performance with a VTAng backup appliance lies in the PCI architecture that is chosen.  Using 64bit/66MHz or better PCI slots for the SCSI Target Mode hardware is critical to outstanding bandwidth performance (i.e. in excess of 100 MB/s), as is the selection of good GbE hardware.  Any GbE controller will work, but to demonstrate great performance, we have purposely chosen a system with an Intel i875 chipset with b uilt-in network controller as our server platform.  This is not a hardware-accelerated solution, as there is no TCP/IP Offload Engine (TOE) involved.  However, because the network controller is embedded in the south bridge, it bypasses the PCI bus and deals directly with memory.  Intel calls this its Communications Streaming Architecture (CSA), and with it, VTAng is able to achieve iSCSI bandwidth performance in excess of 100 MB/s.

With both the SCSI and iSCSI Bandwidth performance in excess of 100 MB/s, the actual sustained transfer rate to a virtual tape drive is limited only by the speed at which data can be tranferred to/from disk.  Here again, there are many variables (i.e. type of disk, rotational speed, SCSI / SATA, RAID or not, etc.), but in our representative system, we see speeds in the 65 MB/s to 70 MB/s range.  Considering that the native transfer rate for the tape device that we are emulating (with compression) is about a third of that, we feel good about claiming that the performance is 2-3 times better than that of physical tape.

1.)  SCSI Bandwidth Performance

Initiator machine:
VTAng-2U-HEAD
Processor:  Intel Xeon 3.06 GHz, 512 KB L2 Cache, 533 MHz FSB
Memory:  1.0 GB DDR, 266 MHz
Boot Drive:  36 GB, 10K RPM, Ultra 320 SCSI
Data Drives:  146 GB, 10K RPM, Ultra 320 SCSI
Networking:  Broadcom NetXtreme GbE
OS:  Windows XP Professional SP2
Application:  Intel IoMeter 2003.12.16

Target machine:
VTAng-2U-HEAD
Processor:  Intel Xeon 3.06 GHz, 512 KB L2 Cache, 533 MHz FSB
Memory:  1.0 GB DDR, 266 MHz
Boot Drive:  36 GB, 10K RPM, Ultra 320 SCSI
Data Drives:  146 GB, 10K RPM, Ultra 320 SCSI
Networking:  Broadcom NetXtreme GbE
OS:  Windows XP Professional SP2
Application:  NexiTech RAM Disk

IoMeter parameters:
Request Size:  512 KB Sequential Access
Queue Depth :  4

IoMeter results:
Read:  114 MB/s
Write:  110 MB/s

2.)  iSCSI Bandwidth Performance

Initiator machine:
VTAng-MT-DISK-SATA-1000
Processor:  Intel Pentium 4 3.0E GHz, 1 MB L2 Cache, 800 MHz FSB
Memory:  1.0 GB DDR, 400 MHz
Boot Drive:  36 GB, 10K RPM, SATA
Data Drives:  250 GB, 7200 RPM, SATA
Networking:  Intel 82547GI CSA GbE
OS:  Windows XP Professional SP2
Application:  Intel IoMeter 2003.12.16

Target machine:
VTAng-MT-DISK-SATA-1000
Processor:  Intel Pentium 4 3.0E GHz, 1 MB L2 Cache, 800 MHz FSB
Memory:  1.0 GB DDR, 400 MHz
Boot Drive:  36 GB, 10K RPM, SATA
Data Drives:  250 GB, 7200 RPM, SATA
Networking:  Intel 82547GI CSA GbE
OS:  Windows XP Professional SP2
Application:  NexiTech RAM Disk

IoMeter parameters:
Request Size:  64 KB Sequential Access
Queue Depth:  16

IoMeter results:
Read:  105 MB/s
Write:  117 MB/s

3.)  SCSI Virtual Tape Performance

Initiator machine:
VTAng-2U-DISK-SCSI-730
Processor:  Intel Xeon 3.06 GHz, 512 KB L2 Cache, 533 MHz FSB
Memory:  1.0 GB DDR, 266 MHz
Boot Drive:  36 GB, 10K RPM, Ultra 320 SCSI
Data Drives:  146 GB, 10K RPM, Ultra 320 SCSI
Networking:  Broadcom NetXtreme GbE
OS:  Windows XP Professional SP2
Application:  Windows XP Backup

Target machine:
VTAng-2U-DISK-SCSI-730
Processor:  Intel Xeon 3.06 GHz, 512 KB L2 Cache, 533 MHz FSB
Memory:  1.0 GB DDR, 266 MHz
Boot Drive:  36 GB, 10K RPM, Ultra 320 SCSI
Data Drives:  146 GB, 10K RPM, Ultra 320 SCSI
Networking:  Broadcom NetXtreme GbE
OS:  Windows XP Professional SP2
Application:  NexiTech VTAng 2.0

Windows XP Backup parameters:
Request Size:   512 KB Sequential Access
Queue Depth:  1

Windows XP Backup results:
Read:  69 MB/s
Write:  65 MB/s

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