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Variable Logical Track Group Management for AIX Logical Volume Manager

IP.com Disclosure Number: IPCOM000202157D
Publication Date: 2010-Dec-06
Document File: 1 page(s) / 25K

Publishing Venue

The IP.com Prior Art Database

Abstract

LTG stands for Logical Track Group. The AIX (Advanced Interactive Executive) LVM (Logical Volume Manager) device driver breaks down I/O requests into units that match the logical track group size, before the I/O is passed down to the device drivers of the underlying disks. Traditionally the logical track group size has always been managed by the administrator. This made sense because the stripe size of the logical volumes was not allowed to be larger than the logical track group size for the volume group. Once this restriction was removed (in AIX 5.3.0) however, logical track group sizes were no longer related to stripe sizes. At that point the optimal logical track group size from a performance standpoint is related to the maximum transfer sizes that the underlying disks will accept.

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Variable Logical Track Group Management for AIX Logical Volume Manager

LTG stands for Logical Track Group. The AIX® (Advanced Interactive Executive) LVM (Logical Volume Manager) device driver breaks down I/O requests into units that match the logical track group size, before the I/O is passed down to the device drivers of the underlying disks. Traditionally the logical track group size has always been managed by the administrator. This made sense because the stripe size of the logical volumes was not allowed to be larger than the logical track group size for the volume group. Once this restriction was removed (in AIX 5.3.0) however, logical track group sizes were no longer related to stripe sizes. At that point the optimal logical track group size from a performance standpoint is related to the maximum transfer sizes that the underlying disks will accept.

However, administrators have always had the ability to add (using the extendvg command) or remove (using the reducevg command) disks while a volume group is online (i.e. without performing a varyoffvg command). On the other hand, changing the size of the logical track group has never been something that administrators can do without bringing the volume group offline and online again (with the varyoffvg and varyonvg commands), at which point the new logical track group size would take effect.

Variable logical track group size automatically selects the optimal logical track group size when the volume group comes...