[CentOS] SSD for Centos SWAP /tmp & /var/ partition

Wed May 25 01:00:54 UTC 2011
Ross Walker <rswwalker at gmail.com>

On May 24, 2011, at 11:40 AM, Bowie Bailey <Bowie_Bailey at BUC.com> wrote:

> On 5/24/2011 11:25 AM, Rudi Ahlers wrote:
>> On Tue, May 24, 2011 at 4:22 PM, Bowie Bailey <Bowie_Bailey at buc.com> wrote:
>>> Personally, I would call it an SATA HDD vs an SATA SSD.  The same would
>>> be true of a SCSI HDD vs a SCSI SSD.
>>> At the moment, if you say "SATA drive", most people will understand you
>>> to mean hard drive simply because the solid state drives are not common
>>> enough.  If the price drops and they start taking over the market, then
>>> the understanding of "SATA drive" will probably change to refer to an SSD.
>>>> From Wikipedia:
>>> Serial ATA (SATA or Serial Advanced Technology Attachment) is a computer
>>> bus interface for connecting host bus adapters to mass storage devices
>>> such as hard disk drives and optical drives.
>> But don't you think that a SSD, or rather Solid State Drive, would
>> still be seen as a different type of drive than a SATA drive, even
>> though they share the same type of bus & connector + power cable?
>> I know you get some USB type SSD's, but people still refer to them as
>> SSD drives, and not USB drives
> We are discussing two different things here.
> 1) What does SATA mean?
> 2) What do people mean when they say "SATA drive"?
> Unfortunately, common language tends to be general and vague.  People
> tend to use terms in ways that are not technically correct -- ever heard
> someone refer to their tower case as a "CPU"?
> Technically, SATA refers to the bus, connector, and power.  Whether the
> general understanding of "SATA drive" will shift when SSDs become more
> prevalent is unknown (but likely).
> Personally, I understand the general meaning of terms like "SATA drive",
> but I know what the technical term actually means and if someone seems
> to be confusing the technical term with the (non-technical) general
> usage, then I will correct them.

A SATA drive can be either a HDD or SSD, the term drive tends to refer to fixed media block device as opposed to say a multimedia (optical) or streaming media (tape) block device. Each device type has it's own particular command set. Though SSD drives and their TRIM command kind of changes things for fixed media devices, but the SCSI PUNCH command has found a common use.

Transport, commands and interface make up the standard. Things get a little strange though when SATA is tunneled through USB or SAS and SATA commands, like TRIM, which don't have a corresponding SCSI command aren't supported, so you can't TRIM a SATA SSD on a SAS controller. The SCSI equivalent to TRIM is PUNCH which is safer then TRIM, but more complex and the two can't interoperate, it is intended to be used in SANs as well as SSDs so the initiators can free up thin provisioned space as needed.