On 9/15/22 03:08, Diego Zuccato wrote:
Il 14/09/2022 19:00, gene heskett ha scritto:
Waiting for 2T SSD's to become affordable, if they ever do.Depends on
your definition of "affordable".
I bought 2 2TB NVMes at about 300€ each... But SSDs and NVMes have a
quite "limited" life. Look at TBW numbers. Many SSDs and NVMes have
some cache RAM for sectors that get rewritten very often, but backups
tendo to be sequential so the cache is nearly useless. Once upon a
time there were flash-backed ramdrives: controller + RAM + SSD +
battery, all the flash contents fitted in the RAM, so the flash was
never written unless the battery got discharged enough. Safe
assumption: battery dicharging = host off = no ongoing writes.
Needless to say the cost was really high and they where usually
reserved for (parts of) databases.
This is where one needs to over-provision. As an example, I have
several rpi4 sized rigs
doing dedicated jobs. Using 8GB cards that were over 50% used got me
card failures quick
enough to get my attention. These cards have internal housekeeping we
can't see, designed
to equalize the wear. So as an experiment the next card I composed for
the rpi4 was a 64Gigger.
This card gets way more than normal read/write traffic as it runs
linuxcnc master, which is
updated several times a week as development goes on. That card, and the
cards in 2 more
rock64's have been trouble free, the rpi4 for 4 years now, and my theory
says its because
they are way over-provisioned, the card has room to do its housekeeping
with zero outward
signs to let me know it is doing anything. Disk usage tools like df show
no loss of capacity, yet
in a typical week up to 3 gigs of it is wiped and rewritten. And has
been since raspian wheezy
on an rpi3. Same card. kernels and linuxcnc from git pulls, but that
gets done on a 240G SSD
plugged into a usb adaptor with only the results being written to the
u-sd. But the 240G is
now at 50% used. How much longer will it last? IDK.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
