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@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.
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