[CentOS] CentOS on SSDs...

Thu Apr 14 09:22:48 UTC 2011
Michael Simpson <mikie.simpson at gmail.com>

On 13 April 2011 18:08, Jim Nelson <jim at broadtime.com> wrote:
> On 4/13/2011 12:28 PM, John Doe wrote:
>> Hi,
>> I was just wondering if there are specific steps to take to install CentOS on
>> SSDs...
>> By example, no swap partition?
>> Format with a flash fs?
>> Sysctl parameters?
>> Thx,
>> JD
> We're running an nginx frontend on SSDs right now - don't bother with things like JFFS2, they're intended for SoC distros that have
> raw flash chips memory-mapped to the controller. Most of that intelligence is handled by the SSD controller.
> CentOS 5 does not have TRIM capability - I'm not sure if CentOS 6 will or not, though. The most important part of setting up SSDs on
> a server is to mount all the filesystems with the noatime option - that reduces the filesystem writes tremendously. Having a good
> controller is equally important - don't run them on a $25 SATA card.
> And, since memory (up to a point) is cheaper than SSDs, fill the box with memory sticks. Keep a swap partition, but put in far more
> memory than you think you will need, and that way you won't hit swap unless the excrement really hits the air mover.  At least,
> that's how we're doing it.
> --
> Jim Nelson
> Systems Administrator, Broadtime
> (888) 582-3229

The MTBF of SSDs and combined with the wear leveling that they use
means that you don't need to worry about them breaking any more. The
more important point is that without TRIM the performance will
significantly degrade as the drive gets used.
I have been using an SSD in a laptop for the last 3 years with CentOS
5 and it works really well and even though the performance did drop it
is still faster than the drive i replaced (very old laptop)
wrt TRIM
This is enabled by default on swap with RHEL 6 but is only available
for other partitions if they are native ext4 and only if you use the
discard option. It therefore won't be switched on for LVM partitions
or any partition or drive using md .
Worth checking that your drive does support it before switching it on.