[CentOS] SSD support in C5 and C6

[Wade Hampton]

I have been following this and have some notes.  Can
you folks comment on them?  I am considering migrating
some systems to SSD but have not had time to set up
a test system yet to verify it.

I found lots of references to TRIM, but it is not included
with CentOS 5.  However, I found that TRIM is in the
newer hdparm which could be build from source,
but AFIK is not included with CentOS 5 RPMS.  That way,
one could trim via a cron job?

Could you folks please comment on the below notes that
I found from multiple sites online.  These are what I was
planning on doing for my systems.  Notes include:

- use file system supporting TRIM (e.g., EXT4 or BTRFS).
- update hdparm to get TRIM support on CentOS 5
- align on block erase boundaries for drive, or use 1M boundaries
- use native, non LVM partitions
- under provision (only use 60-75% of drive, leave unallocated space)
- set noatime in /etc/fstab
    (or relatime w/ newer to keep atime data sane)
- move some tmp files to tmpfs
   (e.g., periodic status files and things that change often)

- move /tmp to RAM (per some suggestions)

- use secure erase before re-use of drive
- make sure drive has the latest firmware
- add “elevator=noop” to the kernel boot options
  or use deadline, can change on a drive-by-drive basis
  (e.g., if HD + SSD in a system)
- reduce swappiness of kernel via /etc/sysctl.conf:

vm.swappiness=1

vm.vfs_cache_pressure=50

-- or swap to HD, not SSD

- BIOS tuning to set drives to “write back” and using hdparm:

       hdparm -W1 /dev/sda



Any comments?

--

Wade Hampton




On Fri, Jul 19, 2013 at 10:10 AM, Alexander Arlt <centos at track5.de> wrote:

> Am 07/19/2013 03:17 AM, schrieb Lists:
> > Main thing is DO NOT EVEN THINK OF USING CONSUMER GRADE SSDs. SSDs are a
> > bit like a salt shaker, they have only a certain number of shakes and
> > when it runs out of writes, well, the salt shaker is empty. Spend the
> > money and get a decent Enterprise SSD. We've been conservatively using
> > the (spendy) Intel drives with good results.
>
> Hm. I'm not sure, if I'd go with that. In my understanding, I'd just buy
> something like a Samsung SSD 840 Pro (for not using TLC) and do a
> overprovisioning of about 60% of the capacity. With the 512GiB-Variant,
> I'd end up with 200GiB netto. By this way, I have no issues with TRIM or
> GC (there are always enough empty cells) and wear leveling is also a
> non-issue (at least right now...).
>
> It's a lot cheaper than the "Enterprise Grade SSDs", which are still
> basically MLC-SSDs and are also doing just the same as we are. And for
> the price of those golden SSDs I get about 7 or 8 of the "Consumer SSD",
> so I just swap those out, whenever I feel like it. Or smart tells me to
> do so.
>
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>