[CentOS] CentOS 6 Partitioning Map/Schema

[Jonathan Vomacka]

Thank you to everyone who responded and contributed to this topic. I 
appreciate it greatly!

On 9/2/2011 12:03 PM, Devin Reade wrote:
> You've already received some good responses so I won't rehash a
> lot of what was said.  However here are few more comments without
> a lot of backing detail (but it should give you enough info to
> google for detail):
>
> 1. Despite the RedHat link someone provided, I think the advice of
>     putting almost everything on the root filesystem is a lot of
>     bunk, at least for servers.  The old arguments for separate
>     filesystems still apply.  I suspect that the single filesystem
>     perspective is coming from desktop scenarios, and especially
>     laptop users and those coming from MS Windows.
>
> 2. Putting /boot on its own filesystem and using LVM for everything
>     else is a generally good idea from both the management and
>     snapshot perspectives as someone previously described.  However be
>     aware that most (if not all) LVM configurations will disable
>     write barriers -- this is probably mostly of interest for when
>     you're running a database.  You need to put on your combined
>     DBA and sysadmin hat, have a look at your underlying disks,
>     disk controller, filesystem stack, database, UPS/powerfail
>     monitoring, and budget to see where your balancing point is.
>     Yes, I have databases on LVM on top of RAID on top of SATA;
>     but it's better to know your risks rather than having them
>     be a surprise.
>
> 3. Pay attention to whether your disks are using the old 512 byte
>     sector size or the new 4k sector size (sometimes called advanced
>     disk format), and whether or not your disks lie to the OS about
>     the sector size.  The RAID, other MD layers, and filesystem
>     need to know the truth or you can run into performance and/or
>     lifespan issues.
>
> 4. Regarding swap: Yes, having it is still a good idea under most
>     circumstances.  The old "2 * physical memory" rule no longer applies.
>     Follow the sizing guidelines from RedHat that someone posted.
>     The kernel is smart enough to use it when necessary and avoid it
>     otherwise.  Having it can get your server through unusual circumstances
>     without crashing but you should have enough memory that you're not
>     paging under normal circumstances.  See also point #6.
>
> 5. Consider encrypting swap.  See crypttab(5), including the comments
>     about using /dev/urandom for the key.
>
> 6. Putting /tmp on tmpfs is a good idea in that it ensures that it
>     gets cleaned out at least when the system reboots.  (Running cron
>     jobs to clear it out periodically can cause problems; under some
>     circumstances.)  This is a good argument to have swap; you can
>     use tmpfs without a significant impact of /tmp using up physical
>     RAM.  Also see the 'tmp' option in crypttab(5).
>
> 7. Under CentOS 5 having less than 2G for /var could cause problems
>     with updates, especially between minor versions.  I've increased
>     my minimum to 4G under RHEL6 due to kdump concerns.
>
> Devin
>
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