Linked by moondevil on Wed 11th Jan 2012 00:10 UTC
Windows The latest blog entry from Steven Sinofsky about Windows 8 describes the Storage Spaces functionality . From the blog entry it seems Windows 8 is getting something ZFS-like. The Storage Spaces can be created in the command line via Powershell, or in the Control Panel for the ones that prefer a more mouse-friendly interface.
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RE[2]: Meh...
by static666 on Wed 11th Jan 2012 07:47 UTC in reply to "RE: Meh..."
static666
Member since:
2006-06-09

Hmm, that's peculiar. It sounds like their "thin provisioning" is really an overcommit feature, where more resources are promised than are available.


Well, overcommit is possible but is a pretty niche feature for big old stupid DBs in server environments where you're better announcing a giant data partition and letting it be initialized at once rather than bring it down for maintenance every time to expand it later.

The more important feature of thin provisioning is that pool space is allocated on the fly to the individual volume requesting it.

Basically, on a 1TB drive you're going to have C: D: E: volumes each reporting 1TB available with their free space shared and you wouldn't need to worry about running of space or wasting it on some volumes. But you will still have 1TB in total, of course. And I'm not sure if Windows will be able to reclaim and reallocate unused space.

In the obvious case of create/read/write calls, they can just return error codes, but it gets much more complicated when memory mapped data manipulation fails (consider the linux memory over-commit solution is the "out-of-memory killer").

It certainly won't panic. Ever tried to add a swap file with holes in Linux? It simply won't allow this. You have to allocate every 0 of it to a real storage.

Reply Parent Score: 3

RE[3]: Meh...
by Alfman on Wed 11th Jan 2012 08:38 in reply to "RE[2]: Meh..."
Alfman Member since:
2011-01-28

static666,

"The more important feature of thin provisioning is that pool space is allocated on the fly to the individual volume requesting it."

To be honest I'm not sure what benefits the "thin provisioning" has to offer over logical volumes.

Certain file systems can already be dynamically expanded as needed without overcommitting them in the first place. The existing data + structures can be used as is within an ever larger volume. This way, no fs re-formatting is needed, just appending more space to the end (LVM is perfect for this).

Unless there is a limitation of the NTFS at play, I'm uncertain why microsoft would chose the overcommitment implementation described since it offers no discernible advantage over a file system that can grow dynamically over it's lifetime.

Another question: Can the pool's size limit ever be changed or is it a hard limit until the whole pool is reformatted?


"It certainly won't panic. Ever tried to add a swap file with holes in Linux? It simply won't allow this. You have to allocate every 0 of it to a real storage."

I wasn't really talking about swap, linux routinely overcommits memory, but the scenario here is a bit different with disk space.

What happens when overcommitted disk resources run out? Windows ought to return an error, but sometimes, as with memory mapped files, that can be tricky to handle. I don't really know what windows does then.

Edited 2012-01-11 08:45 UTC

Reply Parent Score: 3