The following
walkthrough guide runs through an install, setup, and use scenario for NetApp’s
fantastic mbralign tool. The lab used here consists of NetApp 8.1.2 7-Mode
Controller (SIM), VMware ESXi 5.1 Host, VMware vCenter Server 5.1, and VMware
vSphere 5.1 Client. Here we are running VMs on NFS datastores but the theory
applies to FC and iSCSI too. Let’s begin!
1. Download and
install the NetApp Virtual Storage Console for VMware (if not done already)
The software is available from http://support.netapp.com > Downloads
> Software > Virtual Storage Console (VSC). And the latest version of the
VSC is 4.1 which we use here. This post is about mbralign hence the VSC install
is not covered here; for a slightly old blog post that does, please check here!
2. Identifying
Misaligned VMs with the NetApp Virtual Storage Console (VSC)
To run a new scan across whatever datastores are to be
interrogated:
- vSphere client > Home > Solutions and
Applications > NetApp
- Optimization and Migration > Scan Manager
- select Datastores to be scanned and hit ‘Scan selected’
Image: NetApp VSC
4.1 scanning for misalignment (and more)
Then click on ‘Virtual Machine Alignment’, click on the ‘Misaligned’
folder, and review the results.
Image: NetApp VSC
4.1 showing misaligned VMs
Note: The results
of the scan can be seen in various places around the vSphere Client and NetApp
tab, and the scan can be scheduled.
3. Download MBR
Tools
In the vSphere Client, with either: Datacenter, Cluster,
or Host object selected
- select the NetApp tab > Monitoring and Host
Configuration > Tools
- and click on Download to download the correct version of
the MBR Tools for the VMware host in question (options are ESX 4.x or ESXi 4.x
and ESXi 5.x - here we cover ESXi)
Image: VSC 4.1 MBR
Tools Download
Note: From ‘Tools’
you can also download Guest OS Tools
(an iso file containing a script) to set the correct SCSI I/O timeout values (either
60 or 190 seconds) for various supported guest operating systems (Linux,
Windows, Solaris.)
4. Install
mbrtools on the ESXi Host
Note: Recommend
having mbralign and the VM to be re-aligned on the same ESXi host, this is
because mbralign cannot tell power-on status if the VM is on a different host
to the one mbralign is being run from.
With the mbrtools_esxi.tgz downloaded, we need to get this to the ESXi
host, and the easiest way to do this is to upload to an accessible datastore via
the vSphere Client.
Image: vSphere Client
- Datastore Browser with Upload button and mbrtools_esxi.tgz highlighed
Next, before using SSH to connect to the ESXi host, the SSH
service must be enabled via the Configuration tab > Software: Security
Profile > Services and click Properties… > Select SSH and click Options…
> click Start and OK
Connect to the host via SSH (e.g. using PuTTY) and type:
cd /vmfs/volumes
ls
cd DATASTORE_CONTAINING_MBRTOOLS
ls
tar xvzf mbrtools_esxi.tgz
cp -r /vmfs/volumes/DATASTORE_GUID_VALUE_DATASTORE/opt/ontap
/opt/ontap
The above navigates to the correct datastore, unpacks the
mbrtools, and copies them to /opt/ontap.
An example output
(abridged):
~ # cd /vmfs/volumes
/vmfs/volumes # ls
…
LONNFSVOL0
/vmfs/volumes # cd LONNFSVOL0
/vmfs/volumes/51086c31-1b392580 # ls
… mbrtools_esxi.tgz
/vmfs/volumes/51086c31-1b392580 # tar xvzf
mbrtools_esxi.tgz
opt/ontap/
opt/ontap/libshim.so
opt/ontap/mbrscan
opt/ontap/mbralign
opt/ontap/align.bin
opt/ontap/scan.bin
/vmfs/volumes/51086c31-1b392580 # cp -r
/vmfs/volumes/51086c31-1b392580/opt/ontap /opt/ontap
5. Run mbrscan
To check the VM’s VMDK disk alignment status:
- Via the ESXi host CLI, navigate to the folder
containing the VMs disks
- Run the command
/opt/ontap/mbrscan VMDISKNAME-flat.vmdk
Example output
(abridged) - notice the “aligned:No”:
/vmfs/volumes/7ae8613c-c7ea783d/WIN2K3_32BIT_MS_03
# /opt/ontap/mbrscan WIN2K3_32BIT_MS_03-flat.vmdk
…
WIN2K3_32BIT_MS_03-flat.vmdk p1 (NTFS) lba:63
offset:32256 aligned:No
Note: The VM must
be powered off before running mbrscan against the vmdk file.
6. Run mbralign
Note i: Before
running mbralign, it is not a bad idea to take a SAN snapshot of the
datastore/VM folder first.
Note ii: Check out
the Appendix section below for using the --sparse option
if you don’t want mbralign to produce thin-provisioned VMDKs or not make thin
one’s thick!
To run mbralign against a VMDK, via the ESXi host CLI,
run the command:
/opt/ontap/mbralign VMDISKNAME-flat.vmdk
Example output
(abridaged):
/vmfs/volumes/7ae8613c-c7ea783d/WIN2K3_32BIT_MS_03
# /opt/ontap/mbralign WIN2K3_32BIT_MS_03-flat.vmdk
WARNING: This version of mbralign is intended
for ESXi configurations only … This version does not support Windows drive
letter re-mapping. It can only align one vmdk file at a time. Since this
program will not check for space before creating a new vmdk file of
approximately the same size as the original, always check if enough free space
is available in the datastore before running mbralign. The Virtual Machine must
be powered off before running mbralign against the vmdk file. A backup file of
the vmdk file will be created and stored in the datastore alignment occurs in.
If an error occurs, manually restore the vmdk file with the backup.
mbrtools esxi version 1.0
Part
Type old LBA New Start LBA New End LBA Length in KB
P1 07 63 64 16755796 8377866
NOTICE: This tool does not check for the
existence of Virtual Machine snapshots or linked clones. The use of this tool
on a vmdk file that has a snapshot or linked clone associated with it can
result in unrecoverable data loss and/or data corruption.
Are
you sure that no snapshots/linked clones exist for this vmdk? y
Creating a backup of WIN2K3_32BIT_MS_03.vmdk
Creating a backup of
./WIN2K3_32BIT_MS_03-flat.vmdk
Creating a copy the Master Boot Record
Working on partition P1 (3): Starting to
migrate blocks from 32256 to 32768.
12801 read ops in 14 sec. 98.88% read (6.91 mB/s). 98.88% written (6.91 mB/s)
Working on space not in any partition:
Starting to migrate blocks.
100.00 percent complete. 100.00 percent written. .
Making adjustments to
./WIN2K3_32BIT_MS_03-flat.vmdk.
Adjusting the descriptor file.
7. Power up the re-aligned
VM!
As a final check, re-run mbrscan to verify alignment has
worked (the output should say “aligned:Yes”):
/opt/ontap/mbrscan VMDISKNAME-flat.vmdk
Then power on the VM and check all is okay.
Note: There are
additional steps that need to be done with Linux VMs as mbralign messes up the
grub boot loader.
8. Tidy Up
Mbralign leaves a couple of backup files in the VM folder
after the job is complete:
- a VMDK disk descriptor file VMDISKNAME.vmdk-mbralign-backup, and
- a VMDK flat file VMDISKNAME-flat.vmdk-mbralign-backup
Delete these files when they’re no longer needed.
Image: mbralign-backup
files
APPENDIX: Useful
Notes
A. The --sparse
option
Use the sparse option for mbralign to create a thin
provisioned VMDK.
/opt/ontap/mbralign --sparse VMDISKNAME-flat.vmdk
Note: See here for a discussion on
the --spare option not working (making all aligned vmdk’s thick) with the NFS
CopyOffload option enabled.
B. Recovering from
mbralign backup
If the mbralign process didn’t work out, simply run
mbralign again to restore the original. The restore process is very quick!
/opt/ontap/mbralign VMDISKNAME-flat.vmdk
An example output
(abridaged):
/vmfs/volumes/7ae8613c-c7ea783d/WIN2K3_32BIT_MS_03
# /opt/ontap/mbralign WIN2K3_32BIT_MS_03-flat.vmdk
…
Error: A backup file named
./WIN2K3_32BIT_MS_03-flat.vmdk-mbralign-backup was found. This may be from a failed realign.
Please remove or rename all files ending in
-mbralign-backup.
Shall
I restore WIN2K3_32BIT_MS_03.vmdk from the backup I made? y
Note i: This
process also removes the -mbralign-backup files.
Note ii: If you
accidentally turn a thin VMDK into a thick one, the mbralign restore brings
back the thin one!
C. Speeding up
mbralign
Final note!
I came across this tip at http://www.deucedaily.org/blog/2012/03/19/speed-up-mbralign/
regards using a Linux management server to mount the NFS datastore with the
VMDK to be aligned in, and running mbralign from the Linux management server.
Not tried it, but if you’re finding mbralign slow, it might be worth a crack!
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