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[Xen-API] xenserver vhd compression and TRIM instruction

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


[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)

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