Re: [gentoo-user] SSD performance tweaking

[Paul Hartman]

On Wed, Aug 22, 2012 at 4:46 PM, Mark Knecht <markknecht@×××××.com> wrote:
> Hi,
>    Yesterday I got a new, but rather low-end, PCIe-2 SATA-3 6Gb/S
> adapter card and a reportedly high performance 128GB SSD drive. (Links
> below) Other than my swap getting messed up because it didn't use
> labels (who knew about swaplabel but didn't tell me? ;-)  ) the

"mkswap -L name /dev/sdX" :)

> adapter and drive are in the machine and working fine. Unfortunately
> the performance isn't what I might have hoped for. Both hdparm &
> bonnie++ are reporting numbers in the 200MB/S range rather then the
> 400-500MB/S range that I might have hoped for. The machine is PCIx-2
> based according to its specs.
>
>    I'm currently just using a single large partition & ext3. I didn't
> do anything special in fdisk so the partition might not be aligned as
> best it could be. I don't know.
>
>    I'm wondering what sort of experience folks have had trying to get
> performance numbers anywhere close to these specs?

Because it is a PCIe x1 slot card, that is the bottleneck. Based on
all I have read, your speeds are normal and you should consider it to
be the fastest speeds you'll see. If you had bought two SSDs and used
them in a RAID configuration, the speed would actually get worse.

I ran into the same thing a while back, my motherboard actually has
SATA3 on-board, but it is not the primary controller (that one is
SATA2) and it's basically a permanently-installed PCIe controller as
far as speeds are concerned. Because of added latency, the on-board
primary SATA2 is actually faster than the SATA3 when multiple drives
are attached... but it's still faster than a HDD anyway.

I think the only way we'lll see 500MB/sec on that SSD is to buy a
motherboard which has a SATA3 controller as its primary on-board drive
controller and plug it in to that.

Look on the bright side, someday when we upgrade our motherboards,
it'll be like we got a free SSD upgrade for our troubles. :)