[CentOS] SSD support in C5 and C6

[John R Pierce]

On 7/19/2013 8:48 AM, Wade Hampton wrote:
> 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?


trim is done at the file system kernel level.    essentially, its a 
extra command to the disk telling it this block is complete and the rest 
of it 'doesn't matter' so the drive doesn't need to actually store it.


On 7/19/2013 7:10 AM, Alexander Arlt wrote:
> 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...).

those drives do NOT have 'supercaps' so they will lose any recently 
written data on power failures.   This WILL result in corrupted file 
systems, much the same as using a RAID controller with write-back cache 
that doesn't have a internal RAID battery.



-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast