I built an HTPC off of an Asus P8H77-i motherboard. It has dual 60 GB SSDs in RAID1 and 4x 4TB WD Reds in R5. About 6 months ago, I was able to get 600+ MB/s writes on RAID1 and 350+ on RAID5.

However, for some reason I can't track down, now the C drive R1 reports write speeds of 30-40 MB/s and the RAID5 at 70 MB/s. I've played with cache settings in Device Manager and RST and I've tried various RST drivers from 10.x, 11.x, 12.x and 13.x branches.

I'm running Windows Server 2012 R2 on it. I've exhausted everything trying to chase this down. Both R1 and R5 write performance has fallen way down, and surprisingly the SSD R1 is even slower than HDD R5. Using CrystalDisk for performance, I've also had issues copying files between the C and D drives and vice-versa. The performance is very surgey where it goes fast then to 0, then fast again.

Any advice would be appreciated.

Fernando,
Thanks for the assistance, I must have spent two hours on your site last night.

- For SSD, I am using 2 Sandisk "Standard" 64 GB SSDs
- For capcity, I am using 23/60 GB, so it is mostly empty
- I didn't change any BIOS settings, but after I identified the issue, I did update my BIOS since a newer one was released but it didn't fix anything
- I've tried with most items shut off. Basically it is a HTPC so it has Plex, FTP Server (Filezilla), a cloud Backup System, Dropbox, uTorrent and others on it. Since it is Windows Server, there is no Startup tab as things are managed by Services, but I can show you that with pretty much every end-user app disabled/killed, it still doesn't impact performance at all.

I did shut down everything and ran CrystalDisk, just using 50MB since it's fast, but the performance gets worse with larger transfers. Here is a screenshot which has most usable information:
https://dl.dropboxusercontent.com/u/112537/SSD.png

The best I've seen is 710 down and 68 up, but when new, I was getting 900+ down and 400 up.

After I posted, i even broke the RAID intentionally and tested each SSD in degraded alone, the performance was about the same (read was a little lower), but write was stuck at ~30-50 MB/s. I had hoped to degrade the array, convert to normal single disk mode, secure-erase the removed SSD, reattach it and make RAID 1, then break the other one, secure-erase, etc. However, I couldn't find in RST how to convert a degraded R1 array to normal single drive mode.

My D drive which is 4 4 TB HDDs does 400-600 MB/s read and 70-100 MB/s write. It used to write at 400 MB/s + when new. Finally, this is Windows Server 2012 R2, so I'm mostly using Win 8.1 64-bit drivers, but it has worked in the past.

Also, here is a link to CrystalDisk which shows SSD (both SSD report the exact same figures except power on count as for some short time on another system I used one SSD alone):
https://dl.dropboxusercontent.com/u/112537/crystal.png

Trim, NCQ, everything is running. In Disk Optimization I did manually trim it yesterday with no help.

It also shows device manager.

Thanks. It is a Windows Server so it doesn't have a Startup Tab. Server handles startup via services only. I did go into Device Manager and killed just about every non-essential running process without success. Let me look at it again.

MSCONFIG also doesn't show Startup, it just simply isn't something Server supports, but I did disable all unnecessary services and am doing a Minimal Boot.

As far as Device Manager, I have tried every combination of Cache and Flushing. It seems I can get into 70-80 MB/s by having the first box checked but not flushing.

I booted into Safe Mode-Minimal which means no services are running, not even networking. It i the most basic Windows boot environment. The performance is the same, so unfortunately I think it is not related to another program.

I fear my only other method to investigate is to rebuild, but I really don't want to do that. I will try one more thing. I have a USB 3.0 SSD drive, I can see if it performs ok on various machines. I'll report back.

So I used a USB 3.0 SSD drive which regularly does over 250 MB/s, it worked fine on this machine over USB:
https://dl.dropboxusercontent.com/u/112537/USBSSD.png

So it seems performance issue is limited to SATA side and not something inside the system. CPU and Memory utilization are very low on this system. This is why I initially started chasing the IAStorA.sys drivers and found your page. There is something wrong on the Intel side of things, I'm convinced.

Also, I have installed now 4 or 5 different Intel drivers. Is there a good way to clean that out and maybe start fresh, just make sure my drivers are installed absolutely right. For Intel chipset I did an -overall flag because I was stuck with all of these default Microsoft-2006 drivers.

Thanks, for the -overall, for whatever reason I could only get Microsoft provided Intel 7-Series drivers in Device Manager. When I would run the INF installer, it would just go immediately to "Finished". In my case, now I have Intel provided drivers.

Intel emailed me back about my report and said I need to trim each drive outside of the RAID array which is a major pain. I don't have any more SATA ports on this rig so I probably need to remove the SSDs and take them to my other desktop :(

I solved the issue (I think).

Intel was right, and further research seems to elude to that RST doesn't TRIM RAID1 at all (although RAID0 it does). What I did was:

1. Removed one SSD from that system and put it into my desktop
2. Ran CrystalDisk on that SSD as is in the new system, got 40 MB/s write
3. Used SanDisk SSD Dashboard to TRIM that SSD
4. Re-ran CrystalDisk and immediate got 164 MB/s write

After that, I sanitized the disk and put it back in, rebuilt the RAID array (which took only like 2 minutes), then removed the other drive, TRIM'd, sanitized and am now rebuilding it again. So the issue is related to RST especially in RAID1 where it never TRIMs.