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

[Alan McKinnon]

On Sun, 12 Aug 2012 14:11:37 -0400
Allan Gottlieb <gottlieb@×××.edu> wrote:

> On Fri, Aug 10 2012, Alan McKinnon wrote:
>
> > On Fri, 10 Aug 2012 10:25:51 -0400
> > Allan Gottlieb <gottlieb@×××.edu> wrote:
> >
> >> I am getting a new laptop from dell that will dual boot windows (in
> >> case I need dell maintenance) and gentoo (real work).  I have done
> >> this often, but there are three new aspects this time.
> >>
> >> 1.  ssd.
> >> 2.  new udev (/usr part of boot partition?)
> >> 3.  grub2.
> >
> > I have one of those. But I decided to stick with traditional DOS
> > partitioning style and grub instead of GPT and grub2.
>
> I am leaning toward traditional partitioning, but with grub2.  Do
> those two not mix well?

I've never really used grub2 myself (can't see the point until I have
no other option than GPT and EFI), but AFAIK MBR and grub2 isn't a
problem. It might not be default, but it isn't a problem


>
> >> The laptop will have a 256GB ssd.  Can I partition it the same as I
> >> would have for an hd?  Are there extra alignment considerations?
> >
> > I don't know of any special partition considerations. Just start at
> > the 1M mark and align on 4096 like you would for spinning disks.
>
> Dell normally has a special partition of size > 40MB starting at
> sector 63.  Presumably I ignore that one.  I would then align the
> used-only-for-dell-diagnostics windows partition and all linux
> partitions at multiples of 4096

Correct

>
> > What you will need is TRIM support and for that you use ext4. Just
> > add "discard" to the mount options for the ext4 volumes.
>
> Ah so I will now be using ext4.  The mount man page says trim is off
> by default waiting for more testing.  But I will try it.

I think that man page is badly out of date (unless the ext4 devs
understand "testing" to mean something very different to what you and I
understand)

>
> > You also don't need an IO scheduler - ssd access is random like
> > RAM, no heads moving in and out so no sector ordering to worry
> > about. Configure the scheduler as NOOP in kernel config if all
> > drives are ssd's
>
> I believe dell with be "throwing in" a removable spinning disk that
> can be user swapped with the dvd so I should probably keep the I/O
> scheduler.

You can set the scheduler per-device too, more info here:

https://wiki.archlinux.org/index.php/Solid_State_Drives#I.2FO_Scheduler

Someone else reported though that Deadline scheduler can actually
performs better, I also read that somewhere. Maybe you should do some
initial tests yourself before deciding


-- 
Alan McKinnon
alan.mckinnon@×××××.com