R7515 S150 speed limit

Question

Hello,

we recently get an R7515 server with AMD EPYC 7003 series and installing Windows Server 2022. We have 8 HDD in the front and 2 SSD at back. 8 SAS HDD make a RAID5 with PERC H745 Adapter which we named disk D. And 2 Dell Ent NVMe CM6 RI insert in PCIe SSD in Slot 0/1 in Bay 0 which we named disk E and F.

When we use CrystalDiskMark to test the limit speed of the disks, we get the results as follow:

D 1450MB/s 1450MB/s (Read,Write Seq1m Q8T1 speed)

E 6500MB/s 1750MB/s

F 6700MB/s 1800MB/s

everything sound great!

But when we copy large files(2GB+ per file) from disk D to E, the speed can go up to 1.4GB/s.

When we copy large files(2GB+) from disk E to F, the speed can only go up to 400MB/s.

The result is same when we copy from disk D to F or from disk F to E.

We have already tried a few bios setting change and checked the firmware is last updated. We think the NVMe SSD firmware - DELL PERC S150 is the most probably problem.

Could anyone help us understand what happened and try to raise the speed?

DELL-Erman O · Answer

Hello, PERC S150 is a software RAID controller that runs on the host CPU and uses the host memory for RAID operations. Its performance may vary depending on the system resources and configuration. R7515 server supports PCIe Gen 4 which can provide faster data transfer speeds. However, the actual copy speed between NVMe SSDs may depend on other factors, such as the file system, the cache size, the CPU utilization, and the software configuration. You may want to check if these factors are optimized for your system and if there are any bottlenecks or errors that may affect the performance. If you require higher performance for your NVMe SSDs, might be you can consider upgrading to a hardware RAID controller, such as PERC H740P, which is specifically designed for high-performance storage configurations.

zealong · Answer

Thanks Erman

The main issue now can be summarized as NVMe SSDs write speed can go up to 1400MB/s while read speed only can go up to 300MB/s. The result comes from the same file system, cache size,etc.

Usually, the read speed of SSD should faster than the write speed. So what's wrong?

DELL-Joey C · Answer

Hi @zealong,

How are the back 2 SSD connected in the server? Is the rear backplane connected to the front backplane? Eg: Figure 3. Cable routing - 12 x 3.5 inch drive backplane with 2 x 3.5 inch rear drive backplane: https://dell.to/3A729S5. If yes, the 2 drives are supposed to be controlled by H745. Can you check in H745 if it's detected in the PERC H745? Is the H745's firmware up to date? Do you have the 2 Dell SSD DPN#?

zealong · Answer

Thanks Joey I don't think so. Let me show you the picture~

DELL-Erman O · Answer

I can't figure out what is the reason for the direct speed difference. I'm confused. If I were you, I would update the firmware for the first BIOS and the entire SAS chain. Since there can be many factors, we will eliminate them if it is due to outdated FWs. Thanks to Joey, I saw this thread. I'm not sure how much it has to do with it. https://dell.to/3GNXbx7

zealong · Answer

I've two new thoughts about the problem.

One is the system cache settings. When I stop the serveice "SysMain",the speed changed from an equitable approximately about 300-400MB to a fluctuation between 100-800MB. Are there any settings can optimize NVMe SSD reading speed?

The other is that NVMe SSD is mistakenly identified as HDD in TaskManager.With DELL PERC S150 SCSI Disk Device on the upper right corner.(I use the command "diskperf -y" to show speed in TaskManager).Is this one of the possible reasons for slow transmission speed?

PowerEdge Hardware General

R7515 S150 speed limit

Was this post helpful?