[Xen-API] xenserver vhd compression and TRIM instruction

[Denis Cardon <denis.cardon@xxxxxxxxxxxxxxxxxxxxxx>]

Hi everyone,

I would like to hear from you all about the strategies you use to 
compress your VHD file. I mostly use lvmoiscsi shared storage, so the 
VHD compression is not that much for gaining space on the active 
storage, but merely for speeding up XVA exports and transfert.
There is a tool from microsoft for compression [1], but it is Windows 
only and so would require to have access to the VHD file from a Windows 
VM. There is an article on Citrix knowledge database, but with the same 
constraint. Moreover those two articles only talks about NTFS 
filesystem, and not ext3/ext4.
With the new TRIM io instruction for SSD, couldn't it be possible for 
the virtual machine to flag the no-more-used VHD block with TRIM flag, 
so that the vhd compression could happend without needing filesystem 
semantic?
So I'd like to hear from you if you know of anything that could help 
trim unused block from VHD files from xenserver dom0.
Cheers, keep on the good job, and see you in FOSDEM

Denis

[1] http://technet.microsoft.com/en-us/library/hh848458.aspx
[2] http://support.citrix.com/article/CTX133254

--
Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0) 2.40.97.57.55
http://www.tranquil-it-systems.fr


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