Using the Nytro XD Device Node
NOTE This is a Linux-specific chapter. Windows users need not perform any additional steps.
Use the configured Nytro XD device node using the MegaRAID Storage Manager (MSM). For every VD configured in Nytro XD, a new device node is created by Nytro XD. Your applications must make sure that the new device node must be used instead of the original device node for the VD to access the corresponding cached VD in Nytro XD. Nytro XD creates the device mapper device nodes with the same names as the underlying VD names, but with an additional xd- prefix. This device node is placed under the /dev/mapper directory.
For example: If the user issues the following command to configure a VD:
# MegaCli64 XD -AddVd 0x35000c5001d70ae43
Corresponding to the VD, /dev/disk/by-id/scsi-35000c5001d70ae43, Nytro XD creates a node, /dev/mapper/xd-scsi-35000c5001d70ae43, which represents the cached VD. You can find the new device node path using the MSM XD -VdList command.If /etc/fstab contains the following entry, /dev/disk/by-id/scsi-35000c5001d70ae43 /data ext4 defaults 1 2, it must be changed into the following entry:/dev/mapper/xd-scsi-35000c5001d70ae43 /data ext4 defaults 1 2
WARNING When Nytro XD creates a device mapper device node for a VD (for example, /dev/mapper/xd-scsi-35000c5001d70ae43), the same VD is also available for direct access (through /dev/disk/by-id/scsi-35000c5001d70ae43, which is usually a symbolic link to the underlying sd device under /dev for example, /dev/sdg). Even when a cache device (WarpDrive) is configured under Nytro XD, the device node for that (for example, /dev/sdb) is also available for direct access. Exercise caution and make sure that you do not inadvertently directly access or update these disks outside of the Nytro XD control. Such an access is illegal, and any updates made through the direct access can lead to data corruption on these disks. Be aware that this is a feature/limitation of the Linux device model.
DB15-000917-00-May 2012 |
Copyright© 2012 by LSI Corporation. All rights reserved. Advance copy – Not for General Distribution. |