Re: [gentoo-user] VPS has issues emerging everything

[Mark Knecht]

Glad you have a root cause/solution.

On Sat, Jan 8, 2011 at 10:49 AM, Simon <turner25@×××××.com> wrote:
<SNIP>
> The virtual HD is physically on a raid (unknown config).  Mark, the sector
> size issue you mention, does it have to do with aligning real HD sectors
> with filesystem sectors (so that stuff like read-ahead will get
> no-more-no-less than what the kernel wants)?  I've read about this kind of
> setup when I was interested in RAID long ago...  Now that I know my hd is
> actually on a raid, maybe i could benefit some I/O performance improvements
> by tuning this a bit!
>

As it's RAID underneath it's likely set up correctly. The issue I had
in mind was the disk being a 4K/sector disk but the person who built
the partition not knowing to align the partition to a 4K boundary.
That can cause a _huge_ slowdown.

I doubt that's the case here. As this is a hosting service they likely
know what they are doing in that area, and if it wasn't done correctly
you would have noticed it before I think.

> Anyway, I was told by the support team that another user on the same
> physical machine (remember it's a xen VPS) was doing I/O intensive stuff
> which could have "I/O starved" my system.  I don't understand how starving
> or even doing some kind of DoS attack could lead to a complete freeze on the
> console, but eh...

Makes sense actually. The other guy took all the disk I/O leaving you
with none. If you can't get to the disk then you cannot read ebuilds
or write compiled code, or at least not fast.

> They offered to migrate my system to another physical
> machine, and after that...  I was able to perform a complete 'emerge -e
> system' in one shot without a scratch, I even did it with --jobs=2 and
> MAKEOPTS="-j4".  After that, I started a complete "emerge --keep-going
> --jobs=2 world" with MAKEOPTS="-j8"...  (i got 4 cores:  dual xeon 2Ghz)
>

So now you're in good shape...until some user on the new system starts
hogging all the disk I/O and holds you up again.

> This last emerge is still going on as I write this and is emerging pkg 522
> of 620 !!  And there were no build errors so far...
>
> It's emerging glibc at the moment, so once the big emerge is finished, I'll
> probably recompile all pkgs that depend on glibc.  I believe glibc was
> actually updated during my very initial update on monday and I haven't come
> to do that...  but I guess everything will go smoothly from here.
>
> Thanks again for all your help guys!
>   Simon

Good that you got to the root of the problem.

Good luck,
Mark