2012-06-25 02:01 PM
We are starting to use the optimization and migration funcionality in VSC 4.0. After provisioning one datastore via VSC, I moved one VM to this new datastore and started to scan it.
The scan has ended and the VM was put on the actually aligned group. Ok, very nice.
On the scan manager, where I have the list of datastores, that new datastore with the actually aligned VM is listed as NO optimized. Why is that (no optimized)? How does it work?
DOT is 8.0.2P6, VSC 4.0, ESXi 5.0
2012-06-25 07:19 PM
Optimized datastores are the ones created with an offset to align the IO to the misaligned VMs inside it. So it is normal if you have a datastore marked 'No' under optimized that has been created by you through Create Datastore functionality.
After you detect misaligned VM and decide to migrate it using Optimization and MIgration, it will create a new datastore (mark it optimized) with appropriate offset to ensure the IO is aligned. If it finds an existing datastore with the appropriate offset it will move the VM to this datastore instead of creating a new one.
Remember, you should not move aligned VMs to Optimized datastores as it results in the IO becoming unaligned.
Hope this helps.
2012-06-25 07:36 PM
This is a bit confusing. When I provision a datastore through vsc, is it ok that the resulting datastore is one of those not optimized?
Moreover I thought that datastores created within vsc would always be aligned, is it true?
Enviado pelo meu aparelho BlackBerry® da Vivo
2012-06-25 09:34 PM
It's not so much that the datastore is "aligned", but it's more accurate to say that the guests are aligned with the datastore. Typically there are 2 options:
1. Create a datastore in a LUN that is offset to correct guest misalignment
2. Create a standard datastore (with no offset) and correct guest misalignment.
So the real question is - are the guests aligned, or no? If guest parition alignements agree with 4k alignments, then a typical datastore will be just fine. for many Windows 2003/Linux guests, the default alignment is 63 sector/32,256k offsets (unless administrators have taken special precautions to deal with those guest with regards to alignment).
For Win2k8, guests come pre-aligned to suppuort standard datastoers (not optimized). What are you dealign with?
2012-06-26 08:42 AM
I thought that there was 2 levels of alignment. On the datastore level,
between VMFS and storage (which I read once is automatic when creating LUNs
on NetApp specifying the vmware type). And on the guest level between guest
file systems and datastores. Is that incorrect?
On the environment I am dealing with, all the VMs appeared in the
Functionally Aligned group within the optimization tab on VSC. But I have
no optimized datastore. I am trying to understand in which situations those
optimized datastores would appear.
Best wishes and thank you for all the information,
On Tue, Jun 26, 2012 at 1:35 AM, borkp <
2012-06-26 09:17 AM
Actually, you are correct. The VMFS file system should align with block 0, similar to Linux and Windows_2008 LUNs. In addition to aligning VMFS datastore with NetApp, the guests have to be aligned also. As you can imagine, if a guest is not aligned, but it IS in an aligned datastore, I/O will still be misaligned.
I'm not sure with the VSC piece though. Sorry abou that. But you are correct with VMFS and guest alignment. Do you know if the guests are aligned? What O/S are they?
2012-06-26 09:55 AM
Yes the guests are aligned, they are windows 2008. I just don't understand
why my datastore is NO optimized.
On Tue, Jun 26, 2012 at 1:18 PM, borkp <
2012-09-12 10:04 AM
Based on Nick Howell's (NetApp) post on another blog which details this perfectly
Essentially what we’re doing is lying to vSphere, and creating what we like to call a “shim” datastore that is intentionally offset. This way, you just svMotion any misaligned VM’s into this datastore, and the misaligned I/O all of a sudden becomes an aligned I/O stream. Pretty slick if you think about it.
This is to be considered a short-term solution for a much longer “Actually aligned” strategy. Let me be perfectly clear about that. Your VM’s are still misaligned! We’re just aligning the I/O stream under the covers in an online fashion, in order to ease the performance pains of VM’s being misaligned.
Please, still schedule some time to align your VM’s offline with MBRalign, and then move them out of these Functionally Aligned datastores.
2013-04-29 02:14 PM
I have roughly 900 VMDK's that are misaligned.
Of the 900, I'd say 600 of them are offset by 32KB (which is misaligned) and another 100 are offset by16964640KB and a handful of 12289725KB. Dont ask my HOW we got so many, or why certain ones are off set differently
My question is this:
If I create an optimized LUN, I didnt think VSC gave me the option to specify the offset, in which case, it wont work on 200-300 of my VMDK's. If I create a NEW satastore within VSC does the NetApp offset it based on the offset of the VMDK?
If thats the case, I would have to have multiple datastores that are offset differently....