The Dell System Performance Anaylsis team has taken another step in their PERC6 performance analysis work and has included the new MD1120 in a report that covers a very large amount of data. The full paper is posted here in PDF form, this page has the summary and highlights. Please feel free to post questions about this work using the discussion threads at the bottom.

PowerEdge Raid Controller 6 With MD1000 and MD1120 Performance Analysis Report

This paper provides an analysis of the performance of the PowerEdge™ Expandable RAID Controller 6 (PERC 6). The measurement of RAID controller performance is often referred to being an “art” as much as a “science”. Many factors come into play including the controller
itself, the number and type of drives that are attached, the operating system being used, the I/O subsystem of the server and the application in question.

Our performance analysis uses I/O file size, workload type, number of disks, cache enabling/disabling and RAID level as the input test parameters. The reader of this report is expected to be technical wanting to collect more information and/or get an idea about the performance characteristics of this product.

Please see the PERC6 users guide for more product details – http://support.dell.com/support/edocs/storage/RAID/PERC6ir/en/PDF/en_ug.pdf)

Major Advantages

Using 3Gb/s SAS technology, PowerEdge™ Expandable RAID Controller 6 was observed in testing to be able to transfer up to 1484 MB/s (the theoretical upper limit by RAID On Chip (ROC) is better than 1.5 GB/s) using sequential reads and employing both of the external channels. Streaming video and data backup applications are capable of running extremely fast with up to 1MB stripe configurations. This is compared to the previous generation PERC5 with a maximum available 128KB stripe size.

The PERC6 supports all key RAID levels including RAID 6 and 60. RAID 6 tolerates two simultaneous failures, and thus the ability to manage unrecoverable media errors during rebuilds. This is useful especially when many high capacity, half duplex, lower cost SATA disks are utilized.

The battery backed cache offers a large addressable memory space that can increase throughput in several applications and preserves cache contents up to 24 hours using a 7WH Lithium Ion rechargeable battery.

Test Environment

In the tests, Dell Labs used the IOMETER benchmark tool to stress the disk sub-system. With IOMETER we generated 12 different types of workloads to represent different application patterns commonly used by Dell customers. Different application platforms pass data and commands
to the RAID controller in different block sizes. These blocks are called I/O files. To simulate different platforms we used the payload sizes listed below to represent a variety of applications using IO sizes ranging from small to large. The payload sizes were split for graphing to optimize scale of the graph between small patterns with large IOps scores, and large patterns with high MBps but a low IOps scores.

Test Results

The following data is based on extensive PERC 6 IOMETER tests in Dell labs. The graphs following are charted from data in Appendix A of the full paper.

The PowerEdge™ Expandable RAID Controller 6 default operational mode is Write Back No Read Ahead mode. This is due to lower latency times on write activity when in Write Back mode compared to Write Through mode which will wait on the write transaction until the write is complete. For most customers the default settings are preferred, for some customers the default adapter settings may not always offer best performance so Dell gives you a choice.

The PERC 6 offers RAID levels with the choice of stripe sizes 8K, 16K, 32K, 64K, 128K, 256K,512K, and 1MB with the default being 64K. We chose 512K and tested RAID levels 0, 1, 5, 6 and 10. Higher stripe sizes create less physical I/O operations and improve PCI-Express bus
utilization. 512K was selected as it is commonly used in Linux® and was determined to have the best combination of benefit for large I/O and least detriment for small I/O on this controller across multiple Operating Systems. In the following tests, the number of drives used was determined
by the maximum capacity of the storage enclosure under test. The virtual disk count in all tests was 3 or more on the MD1000 and at least 4 virtual disks on the MD1120.

MD1000 Results

The modular design of the PowerVault MD1000 is engineered for easy expansion - giving you more room to store data from your server. Up to six PowerVault MD1000 15 mixed drive expansion enclosures can be daisy-chained together on both channels, giving you up to 90 mixed disk drives options. To keep management simple the PowerVault MD1000 connects to and can be controlled by a single PERC RAID controller equipped PowerEdge server. The following results are a single MD1000 with 15 hard disk drives. The queue depths increase from 2 to 64 outstanding IOs.

The results for RAID 5 MBps and IOPs are shown below. The results for RAID 0, 6, and10 are in the PDF of the full report.

MD1000 RAID 5 MBps



MD1000 RAID 5 IOPs

MD1120 Results

The MD1120 is Dell’s newest storage enclosure. Up to six PowerVault MD1120 24 mixed drive enclosures can be daisy-chained together on both channels giving you up to 144 mixed disk drives options. To keep management simple the PowerVault MD1120 connects to and can be controlled by a single PERC RAID controller equipped PowerEdge server. The following results are a single MD1120 with 24 SAS 2.5” Seagate Savvio 15K.1 drives. The queue depths increase from 2 to 64 outstanding IOs.

The results for RAID 5 MBps and IOPs are shown below. The results for RAID 0, 6, and10 are in the PDF of the full report.


MD1120 RAID 5 MBps


MD1120 RAID 5 IOPs



Please refer to the complete version of the PERC 6 with MD1000 and MD1120 Performance Report for more results and testing details.

Post questions or comments below about the report.