Date: Sat, 20 Aug 2005 17:12:38 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: hselasky@c2i.net Cc: freebsd-hackers@freebsd.org Subject: Re: Parking disk drive heads Message-ID: <20050820.171238.122195775.imp@bsdimp.com> In-Reply-To: <200508201230.37976.hselasky@c2i.net> References: <200508200359.j7K3xoHF015718@ambrisko.com> <20050820031508.A73274@odysseus.silby.com> <200508201230.37976.hselasky@c2i.net>
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In message: <200508201230.37976.hselasky@c2i.net>
Hans Petter Selasky <hselasky@c2i.net> writes:
: On Saturday 20 August 2005 10:18, Mike Silbersack wrote:
: > On Fri, 19 Aug 2005, Doug Ambrisko wrote:
: > > Flash is nice but it has some issues. Atleast dropping it isn't one!
: > >
: > > Doug A.
: >
: > I'd be really happy if I could get a USB flash drive to last more than 8
: > months. Luckily, I started weekly backups after the first failure. That
: > helped a lot when the second failure happened.
: >
:
: Flash drives does usually not last more than 10000 writes, per bit, from what
: I know. Probably you need some kind of special file-system that moves the
: files around as the write quoute gets used up! Eventually the size of the
: disk will reach zero, and you have to move the files elsewhere :-) But this
: is probably off topic.
Actually, 10,000 writes per bit is one or two orders of magnitude too
low these days. It was more typical for the Linear Flash PCMCIA cards
from 10 years ago. Today, typically flash devices are good for more
like 100,000 or 500,000 writes per cell, and all the fobs you'd buy
these days have built-in wear averaging. I've tried three times now
to wear out a flash by writing an incrementing counter to a single
location only to give up after weeks of hammering due to external
factors (power failure, network failure, etc).
Warner
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