Re: [gentoo-user] migrating disks (from mounts to disklabels

[Mick]

On Friday 19 November 2010 19:19:34 David W Noon wrote:
> On Fri, 19 Nov 2010 17:00:04 +0100, Peter Humphrey wrote about Re:
>
> [gentoo-user] migrating disks (from mounts to disklabels:
> >On Friday 19 November 2010 14:42:23 Neil Bothwick wrote:
> >> On Fri, 19 Nov 2010 10:52:50 +0000, Mick wrote:
> >> > Also primary partitions which he does not seem to be using at all
> >> > have a slight edge over logical.
> >>
> >> Do you have any data on this? I generally use all logical partitions
> >> but could be persuaded to rethink.
> >
> >Well there must be one level of indirection on first access, since the
> >start of the logical partition has to be looked up in a "primary"
> >partition, but I can't imagine that being needed more than once per
> >reboot.
>
> Correct.
>
> The same applies to LVM2 or EVMS logical volumes: a small "lookup"
> penalty (a few milliseconds) when the filesystem is first
> activated/mounted, and as fast as the drive itself thereafter.

Short of measuring the latency with some system (which I wouldn't know how) I 
have experimented with setting the /boot partition on primary and logical 
partitions and the difference (on a stopwatch) was measurable in seconds 
betweeen having said partition on a primary and having it on a logical.  
Furthermore, sda7 was slower than sda5.

I haven't measured latencies for first mount and subsequent look ups.  I 
thought that it would be the same every time a partition fs is being accessed, 
no?
-- 
Regards,
Mick