Storage Configuration and Performance

There are keys to the performance of the DV Nation RAMRod that all start with some pretty interesting software configurations.  First up is a little application called Primo Ramdisk that allows you to allocate a portion of your system memory to be used a mountable disk partition. 

While it may look daunting, the configuration is actually pretty straight forward and you can walk through it all with a simple wizard.  Essentially in the screenshot above you’ll see DV Nation created a disk under the label "RAMDISK" and the volume of "R:" (conveniently) with a size of 42GB.  Since our system has 64GB of system memory, a 42GB RAMDisk will leave us with 22GB to play with in other ways, as we’ll soon see.

A RAMDisk needs to have a place to copy all of the data to and from when you reboot or shut the system down to avoid data loss, and you can see that configured to the location of "C:PR_Image.vdf".  In this system build, that location happens to be located on the OCZ RevoDrive 3 X2 PCI Express based SSD to make the copying of data back and forth nearly painless.  If you were copying 42GB of data to your standard hard drive at every boot cycle that would get pretty tiresome though the Primo software is apparently smart enough to only write contents that have CHANGED rather than all contents (using the QuickSave option).  

Though there are many configuration options with Primo, the most important one appears to be the Disk Type set in the screen above.  There are two options: SCSI disk or Direct-IO disk.  Here is how the Primo software describes the difference:

The SCSI Ramdisk is subject to the SCSI specification and more like a physical hard disk. It can be recognized by the Windows Disk Management and almost all other third-party disk management utilities.

The Direct IO Ramdisk is designed for faster access speed. It uses direct I/O method to access data and consequently reduces a lot of internal system transfer and process time which in turn shows better performance than the SCSI Ramdisk. The cost of performance improvement is that the Direct IO Ramdisk is treated as a logical disk by the Windows OS and may not be seen by some third-party disk management utilities. And Direct IO Ramdisk can’t support ReadyBoost feature, as well as VHD feature.

The performance difference can be seen in our testing with CrystalDiskMark – the only benchmark that would properly recognize the RAMDisk in both modes.

First: wow, holy crap!  7.7 GB/s sequential read speeds and 6.9 GB/s sequential write speeds are impressive to see in our testing.  And for our standard 4K test we saw speeds hitting nearly 1.7 GB/s read and 1.3 GB/s writes with a queue depth of 32.  If we compare the Direct IO results to the ones when SCSI mode was enabled you’ll see immediate differences, and large ones, particularly in the 4K graph where performance would drop down to as little as 200-300 MB/s – bah!  That’s like SSD speed…  

We ran some tests on all three of the storage configurations in the RAMRod, the RAMDisk, the PCI Express OCZ SSD and the RAIDed Seagate hybrid drives with AS SSD, ATTO and HD Tach.

The results for this rig continue to impress me, starting with the AS SSD sequential numbers resulting in as much as 4.6 GB/s reads on the RAMDisk, running in SCSI mode.  Check out those access times though – the 18 ms access time of the spinning disks looks horrendous compared to the 0.097 ms of the PCIe SSD and the 0.005 ms (!!) for the RAMDisk.  

Both HD Tach and ATTO, our go to performance metrics for storage devices, show the same kind of scaling from the hybrid drives to the PCIe SSD to the RAMDisk.  

It should go without saying that if you have an application that demands storage performance then DV Nation’s RAMRod PC has the capability to meet it!

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