On Tue, Jun 8, 2010 at 11:27 AM, Joe Auty <j...@netmusician.org> wrote:
> things. I've also read this on a VMWare forum, although I don't know if > this correct? This is in context to me questioning why I don't seem to have > these same load average problems running Virtualbox: > > The problem with the comparison VirtualBox comparison is that caching is > known to be broken in VirtualBox (ignores cache flush, which, by continuing > to cache, can "speed up" IO at the expense of data integrity or loss). This > could be playing in your favor from a performance perspective, but puts your > data at risk. Disabling disk caching altogether would be a bit hit on the > Virtualbox side... Neither solution is ideal. > > Check the link that I posted earlier, under "Responding to guest IDE/SATA flush requests". Setting IgnoreFlush to 0 will turn off the extra caching. > I've actually never seen much, if any iowait (%w in iostat output, right?). > I've run the zilstat script and am happy to share that output with you if > you wouldn't mind taking a look at it? I'm not sure I'm understanding its > output correctly... > You'll see iowait on the VM, not on the zfs server. > Will this tuning have an impact on my existing VMDK files? Can you kindly > tell me more about this, how I can observe my current recordsize and play > around with this setting if it will help? Will adjusting ZFS compression on > my share hosting my VMDKs be of any help too? Compression is disabled on my > ZFS share where my VMDKs are hosted. > No, your existing files will keep whatever recordsize they were created with. You can view or change the recordsize property the same as any other zfs property. You'll have to recreate the files to re-write them with a different recordsize. (eg: copy file.vmdk file.vmdk.foo ; if $?; then mv file.vmdk.foo file.vmdk; fi) > This ZFS host hosts regular data shares in addition to the VMDKs. All user > data on my VM guests that is subject to change is hosted on a ZFS share, > only the OS and basic OS applications are saved to my VMDKs. > The property is per dataset. If the vmdk files are in separate datasets (which I recommend) you can adjust the properties or take snapshots of each VM's data separately. -B -- Brandon High : bh...@freaks.com
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