[geeks] recipe for Linux / iSCSI / thin provisioned space

[Jonathan Groll]

On Tue, Sep 14, 2010 at 10:47:58AM -0500, Jonathan Patschke wrote:
> On Tue, 14 Sep 2010, Jonathan Patschke wrote:
>
>> This avoids the problem of many consumers having gigabytes of disk
>> allotted to them that they don't need and cannot be reclaimed (since so
>> few filesystems shrink elegantly).
>
> A sidenote: I'd hoped that the new "TRIM" commands targeted towards
> flash-based disks would find homes in virtualized environments.  Whether
> you have a VM writing to a VMDK or a client writing to an iSCSI target,
> it'd be Really Nice to reclaim blocks of storage that refer to data
> deleted by the consumer.  This would also let SAN controllers enforce data
> "shredding" policies without consuming CPU time on the consumer and
> bandwidth in-between.

When I was a regular Fusion user I found VMware "unallocated" VMDK
disks to be real space wasters, they just grew in size without an
option for shedding disk space (can't recall what it was that I might
have done [maybe snapshots?] but the option to shrink VMDK disks was
not available). Certainly pre-allocated VMDK disks were much better
for me.

With regard to the OPs question I do know that the IET iSCSI
implementation supports thin disks - 
http://sourceforge.net/apps/mediawiki/iscsitarget/index.php?title=Main_Page
I don't know much about IET though, so don't know if it can be
recommended. 

Cheers,
Jonathan