Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 25 Aug 2009 09:37:12 -0400 | From | Ric Wheeler <> | Subject | Re: [patch] ext2/3: document conditions when reliable operation is possible |
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On 08/25/2009 05:42 AM, Pavel Machek wrote: > On Mon 2009-08-24 20:08:42, Theodore Tso wrote: >> On Tue, Aug 25, 2009 at 01:00:36AM +0200, Pavel Machek wrote: >>> Then to answer your question... ext2. You expect to run fsck after >>> unclean shutdown, and you expect to have to solve some problems with >>> it. So the way ext2 deals with the flash media actually matches what >>> the user expects. (*) >> >> But if the 256k hole is in data blocks, fsck won't find a problem, >> even with ext2. > > True. > >> And if the 256k hole is the inode table, you will *still* suffer >> massive data loss. Fsck will tell you how badly screwed you are, but >> it doesn't "fix" the disk; most users don't consider questions of the >> form "directory entry<precious-thesis-data> points to trashed inode, >> may I delete directory entry?" as being terribly helpful. :-/ > > Well it will fix the disk in the end. And no, "directory entry > <precious-thesis-data> points to trashed inode, may I delete directory > entry?" is not _terribly_ helpful, but it is slightly helpful and > people actually expect that from ext2. > >> Maybe this came as a surprise to you, but anyone who has used a >> compact flash in a digital camera knows that you ***have*** to wait >> until the led has gone out before trying to eject the flash card. I >> remember seeing all sorts of horror stories from professional >> photographers about how they lost an important wedding's day worth of >> pictures with the attendant commercial loss, on various digital >> photography forums. It tends to be the sort of mistake that digital >> photographers only make once. > > It actually comes as surprise to me. Actually yes and no. I know that > digital cameras use VFAT, so pulling CF card out of it may do bad > thing, unless I run fsck.vfat afterwards. If digital camera was using > ext3, I'd expect it to be safely pullable at any time. > > Will IBM microdrive do any difference there? > > Anyway, it was not known to me. Rather than claiming "everyone knows" > (when clearly very few people really understand all the details), can > we simply document that? > Pavel
I really think that the expectation that all OS's (windows, mac, even your ipod) all teach you not to hot unplug a device with any file system. Users have an "eject" or "safe unload" in windows, your iPod tells you not to power off or disconnect, etc.
I don't object to making that general statement - "Don't hot unplug a device with an active file system or actively used raw device" - but would object to the overly general statement about ext3 not working on flash, RAID5 not working, etc...
ric
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