[OpenIndiana-discuss] Appalling disk performance for KVM

[Russell Hansen]

I guess it would appear to be a ZIL related issue.

# zfs set sync=standard

E:\Download>copy sol-11-exp-201011-live-x86.iso c:\temp
        1 file(s) copied.

Version Number:   Windows NT 5.2 (Build 3790)
Exit Time:        2:22 pm, Wednesday, January 4 2012
Elapsed Time:     0:05:42.122
Process Time:     0:00:00.000
System Calls:     970111
Context Switches: 265664
Page Faults:      357801
Bytes Read:       1451203954
Bytes Written:    1440739558
Bytes Other:      3313806348

# zfs set sync=disabled

E:\Download>copy sol-11-exp-201011-live-x86.iso c:\temp
        1 file(s) copied.

Version Number:   Windows NT 5.2 (Build 3790)
Exit Time:        2:24 pm, Wednesday, January 4 2012
Elapsed Time:     0:00:07.578
Process Time:     0:00:00.187
System Calls:     30848
Context Switches: 59859
Page Faults:      353267
Bytes Read:       1440705583
Bytes Written:    1443223804
Bytes Other:      201874527

I'm simply following the recommendations from the SmartOS Wiki
http://wiki.smartos.org/display/DOC/Creating+KVM+Hypervisor+VM%27s

Would it be wise to run with sync=disabled for KVM disks?  Do you *need* to have an SSD SLOG to have acceptable performance for KVM?

-Russ