SCSI to IDE bridges...

der Mouse mouse at Rodents-Montreal.ORG
Tue Sep 23 22:50:02 CDT 2008


>> There are also CF to SD adapters (I've been seeing them in my
>> trolling on eBay today).  There are also the CF form-factor
>> microdrives, but those are getting scarce too I suspect.
> Somehow, I was under the impression that the microdrives were rated
> only for intermittent duty.  Are there any applications that run them
> 24x7 as primary storage?  If not, I sure wouldn't want to consider a
> microdrive as a substitute for a standard-sized hard drive.

In my z50 (which I'm not using at the moment because the 32M RAM addon
croaked, so it's got only 16M instead of 48M, which is close to
crippling) I use a Seagate "8G" (actually about 7.5G) microdrive.

It mostly works fine, but it runs rather hot when it's under even
moderately intensive use (eg, building a new kernel); I suspect it is
designed for a duty cycle in the 10-20 percent range, max.

> Depending on the technology (SLC vs. MLC), around 100,000-500,000, if
> I read the specs right.  Huge for a camera or MP3 player, but not so
> much for, say, a swap file.

Depends.  If it does wear leveling (which I understand almost all of
them do), it becomes a lot more than it appears to be.

For example, if my "8G" microdrive were 8G of CF instead, and had (say)
a write cycle count of 250K writes, that would mean I shouldn't expect
it to wear out until after I've written approximately 250K * 8G, which
is roughly 2PB.  I don't know what microdrive throughput is like (never
measured it on my z50), but at the approximately 7M/s I'm seeing right
now to a "real" disk I'm doing the write phase of a write-read-compare
test over, it takes over 9.7 years to transfer 2PB - and that means
7M/s sustained for the whole 9.7+ years.

That's best-case, not (for example) taking into account that many
writes are smaller than the underlying flash's blocksize.  But even if
you derate it by an order of magnitude, it's still a lot.

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