The new board comes with 4 SATA ports (previous one had only IDE and SCSI) using ICH7R controller which supports RAID 0, 1, 10 and 5, so I decided to see how this built-in solution from Intel handles the 3TB RAID5 array that the Promise cannot. I installed Windows 2008 Standard Server x64 SP2, Matrix Storage Manager 8.8 (latest available from Intel) and the latest driver for Promise controller (2.06.1.326 for Vista/2008).
I created the array using MSM GUI and opened Disk Management console. The array was visible but was split into two partitions: one with size 2048GB and the second one with the remaining 746.41 GB. The default Windows disk – MBR – does not support partitions larger than 2TB. I had to convert the disk to GPT in odrer to have just one partition.
Out of curiosity I tried to do the same operation on the Promise controller, connected the 4 drives, created RAID5 array in the web application (it is not supported in the controller BIOS!) and to my surprise, it behaved the same as on Intel. I could see the whole ~3TB partition! The original server was running 32-bit version of Windows 2003 Server, so first I thought MS is to blame – but only until restarting the server. During the POST, I noticed the Promise BIOS reported the array size as 2199GB and when I logged in and checked the Disk Management, the size was only 2048GB. So obivously there is something wrong with the Promise BIOS. The only way how to use all 4TB of raw capacity is to create two RAID5 arrays (each with size < 2TB) and then – if you want to have only one disk in the system – to create spanned volume accross these two disks. If you make one 3TB array like me it will work only until first restart. And question is if the data written above 2TB will be written properly or it will be just a garbage, eventually it overwrites data stored at the beginning of the disk (as it has happened to me).
And there is one more important thing – the performance of each of this arrays.
First the Promise controller with 4 WD drives, each 500GB in RAID5:
Then the Intel with 4 Hitachi drives in RAID 5:
In both cases the disk cache was enabled, controller cache enabled and NCQ enabled.
I wasn’t able to use the Hitachi drives with the Promise controller as they were already filled with few hundred GB of data, but the WD is not at fault here. The only thing in which the Promise controller is better is CPU utilization. The server is using one Core 2 Duo 6420 @ 2.13GHz, and the performance gain of the Intel is certainly worth the 13%. Not to mention that I don’t have to worry about losing the data again…