I'm sharing a toy

Warner Losh imp at bsdimp.com
Thu Aug 8 14:04:26 CDT 2019

On Thu, Aug 8, 2019 at 12:51 PM ben <bfranchuk at jetnet.ab.ca> wrote:

> On 8/8/2019 12:26 PM, Warner Losh wrote:
> > Even the crappiest of crap SD cards these days aren't that fragile.
> > You'd need to swap on the order of GB/s to wear it out that fast. Most
> > of the SD cards can handle hundreds of full drive writes. At 128GB,
> > you're looking at needing to generate about ~25TB of effective writes
> > before you'd wear them out. Even with a crazy 10x write amp (typical is
> > 2-3), there's no way you'd get that through an interface that's measured
> > in the tens of MB/s.
> I would agree if it was doing a whole disk.
> A swap or scatch space on magnetic media got used alot back then.
> Time sharing back then was having 16KW and swapping pages back and forth
> from rotating media while reading or writing cards.

The NAND pool in the SD cards is rotated to do wear-leveling and to cope
with the insanely large erase block sizes that we have these days, so the
particular LBAs being re-scribbled doesn't matter, though you might get a
lot of write-amp from doing 512-byte I/O when the underlying page size is
4kb or 16kb. Even so, it would take a lot...

> > Warner
> I am not sure of the memory on a PI,but having a good block cache
> for the swap segments on disk would useful.

Agreed. I don't think SIMH forces synchronous writes... A good buffer cache
will mitigate this. I tried to wear our old CF cards w/o disabling the
buffer cache and found it was impossible... But with disabling it, it was
just barely possible, if you did the right things...

> Well the CPU is the easy part. Now what about the front panel. :)

This is purely the dialup experience, eh? :)


> Ben.

More information about the cctalk mailing list