Checking VMFS Patition Alignment

[m7ich7ael7]

I'm checking my alignment with "fdisk -lu". The esx3_partition_align.pdf states "Aligned partitions start at 128. If the Start value is 63 (the default), the partition is not aligned.". I'm a little confused though.

My fdisk -lu output shows a line: (showing a start at 63)

Device Boot Start End Blocks Id System

/dev/sda1 * 63 208844 104391 83 Linux

But a few more lines below it (detailed) shows a start 128:

Device Boot Start End Blocks Id System

/dev/sdb1 128 -1778079812 1258443678+ fb Unknown

Here's my complete output:

# fdisk -lu

Disk /dev/sda: 146.5 GB, 146590924800 bytes

255 heads, 63 sectors/track, 17821 cylinders, total 286310400 sectors

Units = sectors of 1 * 512 = 512 bytes

Device Boot Start End Blocks Id System

/dev/sda1 * 63 208844 104391 83 Linux

/dev/sda2 208845 12787739 6289447+ 83 Linux

/dev/sda3 12787740 16980704 2096482+ 82 Linux swap

/dev/sda4 16980705 286294364 134656830 f Win95 Ext'd (LBA)

/dev/sda5 16980768 21173669 2096451 83 Linux

/dev/sda6 21173733 286085519 132455893+ fb Unknown

/dev/sda7 286085583 286294364 104391 fc Unknown

Disk /dev/sdb: 1288.6 GB, 1288653766656 bytes

255 heads, 63 sectors/track, 156669 cylinders, total 2516901888 sectors

Units = sectors of 1 * 512 = 512 bytes

Device Boot Start End Blocks Id System

/dev/sdb1 128 -1778079812 1258443678+ fb Unknown

Disk /dev/sdc: 1099.5 GB, 1099529453568 bytes

64 heads, 32 sectors/track, 1048593 cylinders, total 2147518464 sectors

Units = sectors of 1 * 512 = 512 bytes

Device Boot Start End Blocks Id System

/dev/sdc1 128 -2147448833 1073759168 fb Unknown

Disk /dev/sdd: 932.0 GB, 932075012096 bytes

255 heads, 63 sectors/track, 113318 cylinders, total 1820459008 sectors

Units = sectors of 1 * 512 = 512 bytes

Device Boot Start End Blocks Id System

/dev/sdd1 128 1820453669 910226771 fb Unknown

Disk /dev/sde: 1099.5 GB, 1099529453568 bytes

64 heads, 32 sectors/track, 1048593 cylinders, total 2147518464 sectors

Units = sectors of 1 * 512 = 512 bytes

Device Boot Start End Blocks Id System

/dev/sde1 128 -2147448833 1073759168 fb Unknown

So am I aligned or not???

MC

[RParker]

Easiest way to align VMFS, is install ESX, installer will allow you to create the VMFS partition DURING install (some say no, I say yes) but you should NOT allow the installer to create the VMFS partition.

Let ESX reboot. Then using the VI Client connect to the ESX host and at that point THEN you configure the VMFS, now it's aligned. If you have ESX 4.0 either way works. So bottom line is ESX 4.0 you are aligned.

I know ESX 4.0 works because I always install ESX from scratch, AND I do everything from the installer, and ALL of my partitions are aligned.

But a few more lines below it (detailed) shows a start 128:

Instructions for VMware VMFS Partition

Alignment Using fdisk

To check that your existing partitions are aligned, issue the command:

fdisk -lu

The output is similar to:

Device boot Start End Blocks Id System

/dev/sdj1 128 167766794 83883333+ fb Unknown

Aligned partitions start at 128. If the Start value is 63 (the default), the partition is not aligned.

If you choose not to use the VI Client and create partitions with vmkfstools, or if you want to

align the default installation partition before use, take the following

[RParker]

Oh yeah this ONLY applies to SAN volumes. Alignment refers to the LUN / Partition alignment. On local disk it doesn't matter where the offset starts, because there is no LUN / Volume to "align" it to.

So the deal is you align paritions ON the SAN, that's all that matters.

[AndreTheGiant]

The first disk used by the installer is not aligned.

And, as written before, may be importan for SAN LUNs.

See also:

Andre