Write performance issue on disk created on RDM disks in VMware Environment
Issue
- extremely slow write performance issue on RDM disks in VMware Environment
- The disk (/dev/sdb) I/O is running around 10MB/s on RDM-P LUN (backend to this is a EMC VPLEX SSD device).
- Either dd or cp commands over logical volume or ext4 filesystem is showing the same 10MB/s throughput.
- There is a slower device (/dev/sda) which is a VMware VMFS backed device (i.e. not an RDM-p mapped vdevice). The same UNIX dd or cp command is seeing about 100MB/s on this device.
Environment
- VMware guest running Red Hat Enterprise Linux 6.5
- gfs2 on VMware RDM-P LUN
- ext4 on VMware RDM-P LUN
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