Tiered Storage Spaces with LSI RAID Controller 9260-8i (no JBOD) - Performance Drop

Question

Hello
I have a Lab-Server with a LSI-Raid-Controller 9260-8i and 2x 256GB SSDs / 6x 600GB HDDs. First I configured the LSI-Raid-Controller with a RAID 1 (2x 600GB HDD) and installed
Windows Server 2012 R2 with Hyper-V Role on this RAID 1. This works just fine. Then I configured the LSI-Raid-Controller with additional 6x "Raid 0 Drive Groups" where each Drive Group has one single physical drive
in it. And then I created 6 virtual drives out of these 6 Drive Groups. So far so good: my Windows Server 2012 R2 now sees 6 new Harddrives (4x 600GB HDD and 2x 256GB SSD). I then created a Storage Pool out of these 6 drives (with PowerShell /
assign MediaType SSD/HDD) and on top of the Storage Pool a "Tiered Storage Space" with Mirror Layout (2x 256GB SSDs mirrored and 2x2x 600GBs  HDD mirrored). This gives me a Tiered Storage Space of about 1.3TB. On this Storage
Space I created a Virtual Drive of 1.3TB capacity. Success!! It seems to work fine.... Even I do not have a Storage-Controller supporting JBOD directly, I was able to create a Tiered Storage Space!!
Now where's the problem? Fine-Tuning the LSI-Raid-Controller Settings and the resulting
Disk Performance....
1) LSI-Raid-Controller: Virtual Drive Properties: What should I choose? Read Policy (Ahead or no) / Write Policy (Write Back with BBU or Write Through) / IO Policy (Direct IO or cached IO) / Disk Cache Policy (enable or disabled or unchanged)
/ Stripe Size (256 KB or ??). Do these settings conflict with the Windows Server Storage Space Layout?
2) Windows Server Disk Management (under "Disk XY"):  Write Cache Policy? (activate Write Cache on this Device) 
3) Windows Server Device Manager (under "Drives" - Microsoft Storage Space Device):  Write Cache Policy? (activate Write Cache on this Device)
4) Performance - Results with Crystal Disk Mark: the inital Results after setting up the Storage were quite good (Seq R: 550 MB/s and W: 590 MB/s //  512K R: 490MB/s and W: 618 MB/s // 4K R: 18MB/s and W: 37 MB/s  //  4KQD32
R:270 MB/s and W:37 MB/S) But 2 months later the values dropped to: Seq R: 290 MB/s and W: 170 MB/s //  512K R: 120MB/s and W: 239 MB/s // 4K R: 1.5MB/s and W: 31 MB/s  //  4KQD32 R: 9 MB/s and W: 71 MB/S). Huge loss of performance
- SSD full? 
5) Since this is a Hyper-V Server I put some VMs on it. The Performance within the VMs has also dropped accordingly. Are there any
best practices when placing VHDX-Files on  a Tired Storage Space? I could of course assign one or two VHDX-Files directly to the SSD Tier, but actually I don't want that because that would use too much SSD-Space.
Any Experts on this Subject?
Mark

Answer 1

Hi Mark,
For the settings of the Raid Controller, it is better to confirm with manufacturer for detailed information. As you said these settings will affect with storage space settings.
From the description you set the 6 disks as 6 RAID0 groups. Is it supported to leave these disks as JBOD and directly add them into a storage space? If Raid settings will affect storage space performance, this could help us avoiding the RAID settings. 
As data is already written onto the virtual disk, we may not available to recreate it. You could have a try with following PowerShell cmdlet to see if it will work better after optimize. 
Optimize-Volume -DriveLetter X -TierOptimize
If you have any feedback on our support, please send to [email protected]