Compact Sco OpenServer 5 guest

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Compact Sco OpenServer 5 guest

Postby AlexL » 23. May 2019, 17:55

Has anyone managed to compact a vdi with Sco OpenServer 5 as guest OS, running on a windows host?

Am using a dynamic vdi, Disk usage was at 37GB, old data was deleted and Sco disk usage went down to about 7GB, but of-course the virtual disk stayed at 37GB.
I have have written a script that fills the disk with as many 2GB files as can fit (HTFS's largest file size) using dd with /dev/zero as input and then deleted them all, used disk space inside Sco went back down to 7GB, the vdi grew from 37GB to 128GB as expected, the max size of the vdi.

My problem is that nothing I do can compact the disk, VBoxManage.exe modifymedium disk sco.vdi --compact runs to 100% but the vdi stays at 128GB, I also tried CloneVDI with same results. I even tried HDD cloning software within a windows guest with the Sco vdi and a fresh vdi attached, using intelligent sector copy, and still ended up with a 128GB vdi.

I suspect the problem is that Virtualbox, clonevdi, windows and the HDD cloning software don't understand the file system (HTFS) in the vdi.

Has anyone ever tried compacting a Sco VM and succeeded? I'm open to any and all ideas. Even if you know of any windows or linux hdd cloning or partition tools that understands HTFS, I'd be keen to check it out.
AlexL
 
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Re: Compact Sco OpenServer 5 guest

Postby michaln » 13. Nov 2019, 10:46

The compaction does not have any understanding of the file system, it works purely on disk sector level. If a sector is full of zeros, it is a candidate for compaction, but there have to be enough zero-filled sectors together for a virtual image block to be eliminated. IIRC in the VDI case the blocks are 1MB, so there has to be an appropriately aligned 1MB chunk of zeros.

What I have seen in the past is that some file system sprinkle control structures throughout the disk, such that compaction can't work because there is no 1MB chunk that's completely empty. OpenServer 5 might be in that category.
michaln
Oracle Corporation
 
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