Comprehensive data protection for all workloads
Gostev
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Re: Version 5

Post by Gostev » Feb 17, 2010 10:49 pm

As far as I know, all those concerns about extents were related to VMFS-2 only... VMFS-3 has most of them addressed.

rogersillars
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Re: Version 5

Post by rogersillars » Feb 17, 2010 11:33 pm

Thanks Anton. I'll ask on another forum, it really would make it easier.

pentana
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Re: Version 5

Post by pentana » Feb 18, 2010 2:34 am

The reasoning for not using extents is because if one of the extends gets corrupted or fails, you lose the whole datastore, as opposed to using separate VMFS datastores.

As the following states, VMFS3 can now use a 64TB LUN rather than the 2TB limitation for the VMFS filesystem itself. This needs to use vSphere though.
The 2TB file limit still stands however with a 8MB block size. Although I imagine if you have a 2TB vmdk something is wrong :)
http://en.wikipedia.org/wiki/VMware_VMFS

Gostev
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Re: Version 5

Post by Gostev » Feb 18, 2010 12:41 pm

pentana wrote:The reasoning for not using extents is because if one of the extends gets corrupted or fails, you lose the whole datastore, as opposed to using separate VMFS datastores.
Actually, from what I know, in VMFS-3 you only loose whole datastore if you lose the first (original) extent. This makes it no worse than "standard" single volume/LUN config. Loosing LUNs backing other VMFS extents will not cause whole datastore loss - the file system will still be accessible.

rogersillars
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Re: Version 5

Post by rogersillars » Feb 18, 2010 7:15 pm

Thanks everyone, I’ve done a bit more research. It appears that ESX supports a maximum LUN size of 2TB, if you want more space then you use Extends. In my case I have a standalone DR server with a 6x 1TB DAS array so when I setup one large LUN for ESX it didn't even display it in the setup. So I setup 2x 1.9TB and 1x 700GB (ish). From my initial research Extends=bad. However after my more recent research that appears to be with VMFS v2, not VMFS v3. So in my case if I lose one array it is highly likely that it would be that multiple disks have failed and it would take out my other arrays also as they are on the same physical disks. When I get a chance I’ll kill the last two data stores and use extends to add the space to the first one. Then it would be much easier to manage and be more flexible.

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