Date: Mon, 22 Aug 2005 00:57:50 -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: <20050822.005750.56564930.imp@bsdimp.com> In-Reply-To: <200508210235.17608.hselasky@c2i.net> References: <200508201230.37976.hselasky@c2i.net> <20050820.171238.122195775.imp@bsdimp.com> <200508210235.17608.hselasky@c2i.net>
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In message: <200508210235.17608.hselasky@c2i.net>
Hans Petter Selasky <hselasky@c2i.net> writes:
: On Sunday 21 August 2005 01:12, M. Warner Losh wrote:
: > 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).
:
: Are you sure that the flash drive is not caching the writes in RAM?
Yes. I'm 100% positive. These devices do not have RAM.
Warner
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