Public bug reported: Currently the code creates a mis-aligned partition on the ephemeral drive during disk creation. This is done by the code attempting to create the partition at the 0 sector which then defaults to 1. When attempting to replicate this setup by hand using parted (as the code does) it will alert you of the misalignment such as:
test@testbox:~# parted --script /dev/xvde -- mkpart primary 0 -0 Warning: The resulting partition is not properly aligned for best performance. This results in the possibility of significantly slower read speeds against the disk, and some impact against the write speeds. The relevant code responsible for the ephemeral partition size configuration can be found at: https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vm_utils.py#L1043-L1057 And the actual parted command utilizing this can be found here: https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vm_utils.py#L992-L1006 I have already committed a simple change for this awaiting review -- Change ID: I2b33659d66ce5ba8a361386277c5fee47ddcde94 https://review.openstack.org/#/c/203323/ Testing for this bug can be accomplished by creating a VM with an ephemeral drive and monitoring r/w speeds with the default partitioning and then with custom partitioning (2048 start sector) using dd/hdparm, etc. ** Affects: nova Importance: Undecided Status: New -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to OpenStack Compute (nova). https://bugs.launchpad.net/bugs/1487300 Title: Misaligned partitions for ephemeral drives (Xenapi) Status in OpenStack Compute (nova): New Bug description: Currently the code creates a mis-aligned partition on the ephemeral drive during disk creation. This is done by the code attempting to create the partition at the 0 sector which then defaults to 1. When attempting to replicate this setup by hand using parted (as the code does) it will alert you of the misalignment such as: test@testbox:~# parted --script /dev/xvde -- mkpart primary 0 -0 Warning: The resulting partition is not properly aligned for best performance. This results in the possibility of significantly slower read speeds against the disk, and some impact against the write speeds. The relevant code responsible for the ephemeral partition size configuration can be found at: https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vm_utils.py#L1043-L1057 And the actual parted command utilizing this can be found here: https://github.com/openstack/nova/blob/master/nova/virt/xenapi/vm_utils.py#L992-L1006 I have already committed a simple change for this awaiting review -- Change ID: I2b33659d66ce5ba8a361386277c5fee47ddcde94 https://review.openstack.org/#/c/203323/ Testing for this bug can be accomplished by creating a VM with an ephemeral drive and monitoring r/w speeds with the default partitioning and then with custom partitioning (2048 start sector) using dd/hdparm, etc. To manage notifications about this bug go to: https://bugs.launchpad.net/nova/+bug/1487300/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
