We have made some changes to the backend SAN Datastore that significantly reduces the I/O congestion, so I don't presently have a need to add multiple datastores to a given vmhost configuration. If that becomes necessary, I will write some code to implement that.
On our system, in addition to moving the workspace datastore to faster disks, I made another change, with which we are currently experimenting. I would be curious to know what you think. I would be happy to submit the relevant changes if there is interest. In looking into the source of this I/O spike, it appeared to be originating from the concurrent creation of the users' default profile in Windows 7. Specifically, at the beginning of a block allocation in which a large number of reservations begin simultaneously -- and therefore each environment copies the default profile at about the same time, this puts a huge I/O load on the backend datastore. The CPU and Memory usage of the server cluster remained very low at the time, but the I/O congestion rendered the VCL almost unusable. What I have done is add an additional field to the image table, where the name of a default user account can be stored. Then, when such an image is created, that user account can be pre-created similar to the steps currently outlined for configuring the default profile [1]. When the image is captured, the account is disabled but not deleted. When a user makes a reservation for the image, this default user account is enabled and a password is set. Then, the user is provided with login credentials for this account. When the user connects to the image, the profile is already setup, and hence the login time is significantly reduced. If the account does not exist on the image, it is simply created anew. I realize that this would not work for systems that integrate the Windows OS-based login with a campus AD backend, and it may be potentially confusing for users who are asked to login to a VCL environment using some arbitrary username (i.e. vcl). Neither of these are issues in our setup, because images are not tied to campus services and users can auto-connect to their reservations (without typing the vcl-generated password), but others may find this unappealing. This also isn't relevant for linux-based images. Aaron [1] http://vcl.apache.org/docs/configure-the-default-profile.html On Jan 11, 2013, at 4:35 PM, Josh Thompson <[email protected]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > If this works best for the backend, I'm good with making it happen on the > frontend. > > Josh > > On Thursday, January 10, 2013 9:35:50 PM Aaron Coburn wrote: >> Hi, >> >> The VCL currently allows VM Host profiles to identify a single "VM Working >> Directory Path", which can be either a dedicated or shared disk. All >> running VMs on a given host will use this datastore path for I/O >> operations. >> >> In our system, we are using a clustered VM host (VMware vCenter) >> infrastructure connected to a shared network (SAN) storage array. In the VM >> host profile, the "Virtual Disk Path" and "VM Working Directory Path" use >> separate datastores, each of which use distinct storage processors in the >> SAN. But still, all running VMs in the cluster use the same datastore for >> their working directories. >> >> We have recently been encountering some significant I/O congestion on the >> host bus adaptors that connect to the VM working directory, resulting in >> really high I/O latency. >> >> My current thinking on this is that I would like to make it possible for a >> VM host profile to identify multiple paths for the "Working Directory". >> This would mean that the path for a given VM would be determined via round >> robin. This would obviously have certain implications for the database and >> existing provisioning module code, as well as involve some front-end GUI >> work. >> >> Do any of you have thoughts on this? >> >> Thanks, >> >> Aaron Coburn >> Systems Administrator and Programmer >> Academic Technology Services, Amherst College >> [email protected] > - -- > - ------------------------------- > Josh Thompson > VCL Developer > North Carolina State University > > my GPG/PGP key can be found at pgp.mit.edu > > All electronic mail messages in connection with State business which > are sent to or received by this account are subject to the NC Public > Records Law and may be disclosed to third parties. > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2.0.19 (GNU/Linux) > > iEYEARECAAYFAlDwhb8ACgkQV/LQcNdtPQOS2ACeMSw188W0zNWv9dSuHdoY/JE7 > OhEAni0ga32Oawpwwcs4wljl21BadzzI > =cyuN > -----END PGP SIGNATURE----- >
