[Open-graphics] [HS] SSD on PCIe

[Nicolas Boulay]

2008/1/24, Paul Brook <paul at codesourcery.com>:
> > Is a ~10 GB SSD on PCIe costly ? It could be perfect for a system
> > disk, the 3Gb/s bandwidth of the PCIe should do the difference with
> > what ever sata disk. You only need to write a Linux bloc drivers (and
> > the mean to boot !).
>
> IMHO this is a bad idea for several reasons:
>
> - The limiting factor for both price and performance of SSD tends to be the
> flash memory, not the interface (unless you're using something really slow
> like USB1).

Sur but it's far more easy to use chips in parrallel than a disk.

> - You need custom drivers.  This makes installation a real PITA. It also means
> yuo have to write and maintain drivers for every OS you support, which is a
> fair chunk of work.

Sur. But for somebody in the Linux kernel dev, it did not look like a
hard point. Then you could use the code for all FOSS code.

> - SATA bandwidth is comparable to a single PCIe lane. If you need more
> bandwidth then it's dead easy to do RAID on the host.
> - Most machines have more free SATA ports than PCIe slots.
> - PCIe SATA cards are cheap.

That's a points. But you avoid a very complexe interface (Pata), for
accessing a quite simple device, a memory chip. I think that you could
also win even more latency. And cheap PCIe SATA card are rapidely
saturated even by HD.

> - Much of the real world speedup from SSD is due to the extremely low latency
> random access (compared to disks), not increased peak bandwidth.

I know. So an increased bandwith will give even more smoothness on the
desktop. I don't understand why there is no chipset to connect few GB
on them.

> Paul
>