Hi,
I have a HA Setup that consists of two Dell R630 ESXI 6.0 Servers that share together a Dell PowerVaul md3800i Fibre Channel Storage.
I am using Linux VMs inside the setup. Some of my apps need the Direct IO (sync writting) and I am getting bad performance here when I test it out.
The BBU Cache is turned on the Storage and when I test it out without Direct IO I get a good performance. When I copy some data inside the Datastore Browser in vSphere Client I get about 600MB/S which is fine for me but with Direct IO I get only 10MB/s. I am using Round Robin for the multiple paths. It happens on every Linux VM Distribution that I use (LSI Logic, Paravirtual etc.)
Here are the test outputs:
dd if=/dev/zero of=mist bs=8192 count=10000 oflag=direct
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 7.93569 s, 10.3 MB/s
Without the flag and Async we get on the same VM a good speed.
dd if=/dev/zero of=mist bs=8192 count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 0.0695623 s, 1.2 GB/s
I was wondering could it be that the ESXI 6.0 does not have a good multipath HBA driver? Or when I am using Direct IO (without the Cache) that the VMs need some special settings there?
Thanks in advacen.
KR
Ultimo