Re: [gentoo-user] new installation (ssd, new udev, grub2)

[Mick]

On Wednesday 15 Aug 2012 17:42:02 Paul Hartman wrote:
> On Tue, Aug 14, 2012 at 9:33 PM, J.Marcos Sitorus <gkjdsh@×××××.com> wrote:
> > Hi guys, after quick read about ssd, I have a couple of question:
> > 1. My friend have new server with a ssd installed. He plan to RHEL 5.7
> > (I don't know why he choose this) on it. On redhat website, it say
> > something like this:
> > "However, if the device does not export topology information, Red Hat
> > recommends that the first partition be created at a 1MB boundary."
> > What does it mean by 1MB boundary? Does it mean he have to create 1MB
> > free space in front or he have to create a 1MB partition in front of
> > his actual partition(s)?
>
> When you run fdisk and it asks starting sector, choose one that has
> 1MB of free space in front of it. Flash memory, like magnetic disks,
> writes and erases in blocks, so improper alignment can cause multiple
> read/writes to happen when only one should have been necessary. Most
> flash-based memory has erase blocks with multiples of 4MB so I always
> begin the partition at 4MB to be safe. Magnetic disks have much
> smaller blocks so 1MB is the usual recommendation for those (since 1MB
> is safely divisible by 64k/32k/16k/8k/512b etc.) though if you know
> the actual block size on your disk you can go smaller than 1MB.
>
> > 2. Is it possible to combine TRIM support and ext3 partition (AFAIK,
> > RHEL 5.7 haven't support ext4)?
>
> Basically no. Depending on kernel & everything else version there
> might be offline trim support ioctl, but not automatic. Don't know
> anything about RHEL but maybe xfs supported TRIM in that version.
>
> > *i hope this is not count as hijacking
>
> Don't know if it is hijacking, but it is not an RHEL list, and
> top-posting can get an angry mob started. :)

Grrrrr!  :@

LOL!

Anyway, I am told that Gparted now adds a 1M unallocated space before a 
partition is created (and shows it too) as long as one leaves the default 
alignment option of 'MiB', rather than 'cylinders'.

I'm not sure what it does if you select cylinders.  May still create it, but I 
seem to recall that older versions of Gparted did not show unallocated space 
less than 8M.

I think that current versions of fdisk also provide a 1M boundary, or is it 
4M?  Someone more up to speed on this can comment.
-- 
Regards,
Mick