Richard Elling wrote:
Greg Palmer wrote:
Miles Nordin wrote:
gm> That implies that ZFS will have to detect removable devices
gm> and treat them differently than fixed devices.
please, no more of this garbage, no more hidden unchangeable automatic
condescending behavior. The whole format vs rmformat mess is just
ridiculous. And software and hardware developers alike have both
proven themselves incapable of settling on a definition of
``removeable'' that fits with actual use-cases like: FC/iSCSI;
hot-swappable SATA; adapters that have removeable sockets on both ends
like USB-to-SD, firewire CD-ROM's, SATA/SAS port multipliers, and so
on.
Since this discussion is taking place in the context of someone
removing a USB stick I think you're confusing the issue by dragging
in other technologies. Let's keep this in the context of the posts
preceding it which is how USB devices are treated. I would argue that
one of the first design goals in an environment where you can expect
people who are not computer professionals to be interfacing with
computers is to make sure that the appropriate safeties are in place
and that the system does not behave in a manner which a reasonable
person might find unexpected.
It has been my experience that USB sticks use FAT, which is an ancient
file system which contains few of the features you expect from modern
file systems. As such, it really doesn't do any write caching. Hence, it
seems to work ok for casual users. I note that neither NTFS, ZFS,
reiserfs,
nor many of the other, high performance file systems are used by default
for USB devices. Could it be that anyone not using FAT for USB devices
is straining against architectural limits?
-- richard
The default disabling of caching with Windows I mentioned is the same
for either FAT or NTFS file systems. My personal guess would be that
it's purely an effort to prevent software errors in the interface
between the chair and keyboard. :-) I think a lot of users got trained
in how to use a floppy disc and once they were trained, when they
encountered the USB stick, they continued to treat it as an instance of
the floppy class. This rubbed off on those around them. I can't tell you
how many users have given me a blank stare and told me "But the light
was out" when I saw them yank a USB stick out and mentioned it was a bad
idea.
Regards,
Greg
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