Re: Solid State Drives with PG

On Wed, Apr 7, 2010 at 3:27 PM, Vick Khera <vivek(at)khera(dot)org> wrote:
> On Fri, Mar 26, 2010 at 3:50 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>> here is a _used_ 320gb ramsan for 15k :-).  dram storage is pricey.
>>
>
> I think using DRAM as the base is way better than flash.  Just use the
> flash or a regular disk as the backup with a battery to power the
> backup operation.
>
> I have in my storage room a DRAM based SCSI storage device made by
> Imperial Technology.  It was totally the bees knees in 2000 when I
> bought it (with 1GB of RAM) for almost $30k.  Upgraded a year later to
> 5Gb for another $15k.  It has 4 low-profile/offset SCSI-2 connectors
> and full battery backed up UPS internal to it, and writes itself to a
> traditional disk drive on power outage, and continually ran self
> diagnostics to ensure that everything was just right.
>
> Free.  But it doesn't power up.  Probably needs a cap replaced or
> something simple like that.

dram storage makes sense in some cases but is generally so expensive
that it throws off the whole hardware cost/engineering calculus even
with the insane expense of writing software (even to the 0.0001% of it
managers that understand this). that's saying something.

the idea behind flash storage though was to provide at least decent
performance at a reasonable cost. making dram storage fault tolerant
takes a lot of engineering thus the high cost. as a dba, the idea of
flash being able to be swapped in for sata spinning drives for a
10-20x gain in iops makes me vibrate.

except that the fault tolerance issue isn't worked out yet. so I
continue to buy bulk fossilized dinosaur plop and waste precious time
figuring out how to make it work with otherwise fairly modern
equipment. did i mention that i was annoyed with intel?

check out their faq entry on ssd/write back cache:

Does the Intel SSD have a write cache?
Yes. However data caching is limited to the controller for enhanced performance.

huh!?

merlin