On 24/10/2014 1:59 PM, Orion Poplawski wrote: > On 10/22/2014 03:23 PM, Steven Haigh wrote: >> Hi all, >> >> I'm wondering - I'm looking to simplify my Xen DomU installation via a >> kickstart file... >> >> As my Xen config has /dev/xvda - which should be formatted as ext4 and >> used as / - is there any options that I can achieve this? >> >> Just about everything I've stumbled across does partitioning first - and >> not the entire disk. Without supplying a kickstart file, the installer >> will bail saying no disks found. >> >> It's been this way for MANY years, but I heard rumours of a magical >> kickstart option - but I can't seem to find it... >> > > What do you have against partitioning the disk? Loosing the 512-bytes > for the partition table?
On some setups it can cause major write degradations in the virtual machine. If you can imaging the disk being set up in 4Kb clusters - which LVM then adheres to - but on the DomU disk with a partition, the alignment for partition data is now 0 + 512 bytes instead of 0. This means a write of 4Kb would write two sectors to the physical disk (first being 512 bytes + 4Kb, the second being the 512 bytes that give us an offset). In lame ASCII art, this means: Plain Disk: 0-----------512-----------1024-----------1536-----------2048 etc Whole disk write: ----------------------------------------------------------> to 4Kb Partitioned disk write: [ part tbl ]--------------------------------------------> to 4Kb + 512 bytes Its good to get your sectors aligned.... Especially when its on a RAID backend that also has a stripe size as well... -- Steven Haigh Email: net...@crc.id.au Web: http://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897
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