Dell Perc 6i
The Dell Perc 6i is a PCIe x8 SAS/SATA RAID card fitted to many Dell PowerEdge servers such as the R610 and R710. The card superceeds the earlier Perc 5i controller and has several improvements:
- RAID 6 and 60
- Support for SSD drives (see transition guide)
- SATA NCQ
- Lower power consumption
The card supports RAID 0, 1, 10, 5, 50, 6 and 60 and is reasonably priced on eBay considering the performance of the card.
The card is also available with external connectors (the Perc 6/E) and a cut-down version (the Perc 6/iR) which has no cache and supports only RAID 0 and 1.
Contents |
Specifications
- Device Type: Serial Attached SCSI Raid Controller Card
- Interface Type: x8 PCI Express 1.0
- Processor: LSI 1078 RAID-on-a-chip (ROC)
- Cache Size: 256MB fixed (256MB or 512MB removable modules on the 6/E)
- Channel Qty: 8
- Port and Connector Type: 2x SFF-8484 (6/i), 1x SFF-8484 (6/iR)
- RAID Levels: 0, 1, 5, 6, 10, 50, 60
- Drives supported: 144 (6/E), 16 (6i), 4 (6/iR)
Connectors
The card has two SFF-8484 connectors providing direct connection for 8 SAS or SATA drives, with appropriate cables, or connection to a hot-plug backplane (providing support for 16 drives).
The cut-down 6/iR card has one connector and supports only 4 drives.
Performance
Performance, according to Dell documentation based on an MD1120 with 24 15K SAS drives are approximately:
| RAID Level | Sequential Read (MB/s) | Sequential Write (MB/s) | 8K Random 70% read (IOPS) |
|---|---|---|---|
| 0 | 810 | 1050 | 6,300 |
| 10 | 810 | 510 | 5,050 |
| 5 | 800 | 480 | 3,200 |
| 6 | 800 | 375 | 2,800 |
Some versions of the firmware show very poor performance with RAID-0, which has been corrected in A11 firmware.
The card can run much higher random 4K IOPS with SSD drives, running a single SandForce 1200 drive near its controller limit at around 20,000 IOPS read and 12,000 IOPS write. Sequential read is inline with expectations at 255MB/s, but write performance is poor at about 60MB/s regardless of write cache policy.
SATA NCQ is supported.
Firmware
The latest Dell firmware is available from dell.com.
Fittment to Unsupported Machines
When used in a machine other than an officially supported PowerEdge server, additional cooling must be provided as the heatsink fitted to the LSI ROC processor is dependent on forced airflow. A large northbrige heatsink is usually sufficient, especially if in the flow path of a case fan.
The card can be fitted to most systsms, but when used in systems with certain nVidia chipsets (such as the HP ML115 G5 server), the chipset SATA ports and any RAID functionality must be disabled in the system BIOS. Without the ports disabled, the system may boot successfully but the <CTRL-R> BIOS utility will not function. Note that the ML115 G5, ports 0/1 can be left enabled.
Cache and Battery Backup
An optional 7w LiIon battery provides up to 72 hours of backup to the cache in the event of power failure. If power is restored within this time, uncommitted writes are flushed in the controllers BIOS phase (a 'dirty cache' LED on the board indicates that data will be flushed at next power on).
The battery and cable are interchangable with that available for the Perc 5i controller, which are available as service kit XJ547.
The 6i card has directly mounted RAM and hence the 256MB cache cannot be upgraded. The 6/E however has a 'transportable battery backup unit' which can be upgraded from 256MB to 512MB. The low-spec 6/iR controller has no cache fitted and cannot be upgraded.
Limitations
With RAID-10, RAID-50 and RAID-60, only one LUN can be created on a drive grouping and this must occupy all available space. As a result the 2TB limit for BIOS based computers can easily be broken with these volumes, rendering them unbootable on systems without EFI.
This also causes problems with vmware ESX and ESXi, since the maximum volume supported at least up to v4.1 is just under 2TB.
