Re: [Iscsitarget-devel] support for virtualbox

[Ross S. W. W. <RW...@me...>]

Turbo Fredriksson [mailto:tu...@ba...] wrote:
> On Dec 12, 2012, at 3:34 PM, Ross S. W. Walker wrote:
> 
> > Dedup is slower than sparse files, but I don't think the issue the OP
> > mentions has to do with duplicate data, but wasted space from thick
> > allocation (unused data).
> 
> > If you have cloned VMs though using ZFS cloned sparse zdevs could
> > provide both performance and space savings.
> 
> So sparse + dedup is a very nice combination that isn't available
> (stable) in any other FS that I know of.

There are storage solutions though from EMC, NetApp, Compellent and
others that can provide sparse (thin provisioned) and deduplicated
volumes through FC, iSCSI, FCoE and CIFS/NFS, so it isn't the only
game in town.

All VMware ESX VMDK files on top of NFS shares are thin, so if you
use a ZFS deduplicated volume over NFS then it will be both thin
and deduplicated by default.

My personal best practice is to store VMDK files on NFS and put
application data on RDMs using block storage protocols such as
FC, iSCSI or FCoE. To that end ZFS is best for those NFS VMDK
volumes of gigantic size. ZFS's self healing and data integrity
checks are a life saver for those volumes that are too big to
backup. Please note, that setup works for us because we have
redundant virtual servers in multiple data centers with
application data replicated and backed up in each data center.

-Ross

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