RAID CONTROLLER CONFIGURATIONS
Finding the best settings for each card is a time consuming task as all controllers react differently depending upon firmware implementation. Both controllers utilized a 64k stripe size. Considerable optimizations can be made in regards to performance by varying the stripe size but there are simply too many configurations to test for the purposes of this report.
LSI 9265-8i: FastPath recommended settings of Write Through, No Read Ahead, and Direct I/O
Adaptec 6805: Dynamic mode, NCQ enabled, with Write Back caching enabled. Read Caching is also enabled.
As can be seen throughout the review, there are some large differences in performance and we did try every conceivable combination of settings in an attempt to boost the performance. In many cases there simply wasn’t enough of a difference in the respective tests to warrant changing the settings. We did utilize a wide range of settings with the 6805 in particular, in attempts to eke out more performance. In the end it was best to leave the controllers on settings that performed the best over a wide range of tests.
We will be using Iometer extensively for IOPS testing. Some of the metrics are hard to benchmark outside of real applications so there will be some charts with an explanation of real world results. As always, any and all configurations should be evaluated and administered by a storage professional, thus being optimized for the workloads involved.
For SSD testing we will be utilizing the WEI benchmark, Anvils Storage Utilities, AS SSD, PassMark, and of course our staple of testing, PCMark Vantage.
OF SPECIAL NOTE
The Lightning LS 300S drives aren’t your standard equipment. In order to receive maximum performance with one controller the devices have to be configured in WidePort mode, which essentially uses two connections to one drive. It is, in essence, like having two devices connected in one. The SAS expander we are using does support two connections to each device through failover mode. The typical expander does not support the WidePort function in the capacity that the SanDisk uses it, so we sourced some special cables to enable us to get the job done. Using these cables we were able to connect to the rear of the expander, and use it as a pass through device to carry the data through the expander and into the RAID controller. This is where the ability to daisy-chain the ARC-4036 really came in handy!
Here is a ‘mock-up’ of how we ran the drives with the LSI controller. The top two SAS cables went to the RAID controller, and the bottom two cables were used to connect the SanDisk drives. The typical set of cables will allow four devices to be connected to each cable, but the special DualPort cables we used actually uses two ports per device, for a total of two drives per cable. In this configuration we can leverage both the awesome power of the SanDisk Lightning LS 300S drives and the Mercury Extreme Pro SSDs at will.
We did run into a compatibility issue here on this front with the Adaptec controller. The Adaptec does not support the Areca 4036 enclosure expander ports, which is curious. The Areca SAS expander module is the LSI 28-port LSISAS2x28 expander IC which is a very commonly used expander in a variety of devices. It is surprising, to be honest, that the Adaptec does not have support for this type of enclosure.
It is to be understood that of course the LSI card will work with its own expander IC, but one would expect that such a widely used IC would be supported by Adaptec as well.
To determine whether the incompatibility lies with the SanDisk EFDs or the Areca enclosure, we connected an array of standard SSDs to the rear ports of the enclosure. Unfortunately any devices connected to the expander ports were not recognized by the Adaptec controller. This could be seen as troubling if one were to consider the implications of incompatibility with widely used expander modules.
Queries with Adaptec Support regarding compatibility issues with this configuration were unfortunately not very fruitful. We were merely informed that this device was not compatible with the enclosure. There haven’t been any firmware upgrades of the Adaptec controller since April of this year, which is quite a bit of time considering the amount of new devices constantly coming into the marketplace.
The problem became our cables. Surely if one were to connect the SanDisk drives directly to the Adaptec controller we could use them for testing. The special dual port cables that we are using for testing utilize an 8088 MiniSAS connector, which is compatible with our enclosure. The connections on the Adaptec are the internal 8087 connectors, so we did source an adapter to allow us to move forward with a direct connection to the devices.
Using a 8087 to 8088 adapter we were able to connect the dual port sas cables with the MiniSAS cables to a pair of standard 8087-to-8087 cables. These cables were then attached to the Adaptec controller, and off we go!