Re: inferior SCSI performance

Christopher Browne kirjutas K, 01.10.2003 kell 19:21:

>
> The FS-related result appeared surprising, as the "stories" I had
> heard suggested that JFS hadn't been particularly heavily tuned on
> Linux, whereas XFS was supposed to be the "speed demon."

Gentoo linux recommends XFS only for SAN+fibre channel + good ups for
anything but database use ;)

> It is entirely possible that the result I saw was one that would
> reverse partially or even totally on a system LACKING that cache. XFS
> might "play better" when we're cacheless; the (perhaps only fabled)
> demerits of JFS being more than totally hidden if we add the cache.
>
> What I find disappointing is that it isn't possible to get SSD cards
> that are relatively inexpensive. A similarly fabulous performance
> increase _ought_ to be attainable if you could stick pg_xlog and
> pg_clog on a 256MB (or bigger!) battery-backed SSD, ideally one that
> plugs into a PCI slot.

For really cheap and for small-size transactions you could experiment
with USB2 memory sticks (some of them claim 34MB/s write speed), perhaps
in striped/mirrored configuration. You would just need something
counting writes in the driver layer to alert you when you are reaching
the x00k "writes" limit and have to plug in new sticks :)

OTOH, articles I found through quick googling suggest only 2.4MB/s write
and 7MB/s read speeds for USB 2.0 memory sticks, so the 34MB is proably
just sales pitch and refers to bus speed, not actual write speed ;(

> Unfortunately, while there are companies hawking SSDs, they are in the
> "you'll have to talk to our salescritter for pricing" category, which
> means that they must be ferociously expensive. :-(.

the cheapest I found was the one with external backup power was ~1.8k$
for 2GB PCI device

http://www.cdw.com/shop/search/Results.aspx?key=platypus&x=0&y=0

An external 16GB one with battery backup and
write-t-small-ide-drives-on-power-failure was ~25k$

-----------------
Hannu