There's a VM with guest OS window 2012R2 running as SQL DB server. The VM have 4 virtual volumes. The VM recently have problem copy a file that's around 10GB size on one of the volumes. After copying the file until 30% with the average speed of 300MB, the straight drop to 0MB then the speed becomes slow around 20MB. I tried the same file on other volumes at the same VM and it was able to transfer completely in 10 minutes. The VM is reside in one of the ESXi host in a vCenter cluster environment where it has 2 ESXi nodes. Both ESXi is connected to a SAN Storage provisioned with 3 datastores.
Any ideas on how to find what causes this VM problem?
Sounds like you're hitting some limit on your SAN; maybe filling up the write cache?
I don't know what type of SAN you're using, but I would try to see what it's monitoring tools can tell me about the situation.