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? :)
Warner
Ben.