[Xen-users] 4KB Sector Disks

[Gordan Bobic <gordan@xxxxxxxxxx>]

I just thought I'd mention this because it turned out to be the cause of 
disk I/O performance issues I've been having. For the arhchive/search 
engines of nothing else.
Setup:

Storage server (Linux):
1) ZFS zvol backed images, ZFS configured for 4KB sector disks
2) IETD iSCSI server

dom0 (Linux):
3) Open-iSCSI client (Linux)

domU is Windows.

When 2) is set for 4096 byte sectors, the performance is terrible, and 
qemu-dm tops out at about 5MB/s when it hits the CPU limit. Reduce it to 
512 bytes, re-partition accordingly to ensure the partition is 4KB 
aligned, and the performance goes up massively. Booting up domU now 
takes seconds rather than minutes, and doing the 
fresh-install-millions-of-updates update takes minutes rather than hours.
Something in the stack really seems to grind to a halt when dealing with 
4KB physical sectors at the moment. Nothing breaks or warns, it just 
runs really slowly.
Gordan

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users