Linked by Thom Holwerda on Thu 13th Jun 2013 14:35 UTC
Mac OS X The third and final WWDC product I want to talk about is - of course - OS X 10.9 Mavericks. While iOS 7 was clearly the focus of this year's WWDC, its venerable desktop counterpart certainly wasn't left behind. Apple announced OS X 10.9 Mavericks, the first OS X release not to carry the name of a big cat.
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RE[2]: Interested in compression
by malxau on Thu 13th Jun 2013 19:13 UTC in reply to "RE: Interested in compression"
malxau
Member since:
2005-12-04

I don't. When NTFS crashes it can be far more subtle, let's say a cluster bitmap corruption (i.e. the bit that tells the filesystem what space is used and what is free). Ever seen that?


So firstly, I work on Windows filesystems (see bio.) I get to see a lot...

It looks, on the users' end, like files are randomly disappearing as they're being erased by new files without the os realizing it.


I don't think this is what happens. Imagine a cluster is in use by FileA but (for whatever reason) the bitmap doesn't record it as allocated. Now FileB gets allocated the same cluster. FileA is still there, because the system didn't detect the condition. It's just that FileA's contents end up the same as FileB's contents, because they're using the same block. And if only one cluster was in this condition, the party stops here, because the cluster is now marked in use so only these two files will share it.

Given how bad this is, NTFS works hard to avoid it, both at the design level and by making pessimistic assumptions in event of detected corruption. As above, I see a lot, and I don't see this often.

...like the ext? filesystems and zfs, it is self-correcting as there are multiple copies of the superblock and inconsistencies are checked against them.


ZFS has checksums so it can detect corruption in its structures (assuming, of course, that the corruption was not generated by a bug), and use a good copy if one exists. ReFS, Microsoft's next generation file system, also checksums its metadata, and when used with Storage Spaces can also locate a good copy of data if one exists. Ext2/3 do not. Ext4 checksummed its journal and more recently metadata too; I don't know how it would be able to recover though, since AFAIK it doesn't keep redundant copies, so it has nothing to recover from.

Reply Parent Score: 5

rekabis Member since:
2010-02-25

I don't. When NTFS crashes it can be far more subtle, let's say a cluster bitmap corruption (i.e. the bit that tells the filesystem what space is used and what is free). Ever seen that? It looks, on the user's end, like files are randomly disappearing as they're being erased by new files without the os realizing it.

Given how bad this is, NTFS works hard to avoid it, both at the design level and by making pessimistic assumptions in event of detected corruption. As above, I see a lot, and I don't see this often.


I have been working with computers since 1982, on the Internet since 1988, on the Web since 1992, and in the I.T. sector since 1997. I have enjoyed the Windows NT line of computers ever since NT 4.0 was released (got my first copy late 96), and I have *NEVER* seen something like this happen. And I have repaired thousands of NTFS-based Windows computers and Windows installations in my day from 4.0 clear up to Win8.

Was I just lucky? *knocks on wood*

Edited 2013-06-13 20:29 UTC

Reply Parent Score: 3

Bill Shooter of Bul Member since:
2006-07-14

I think there are certain patterns of use which make the situation more likely that sane people try to avoid for other reasons. I've seen simuluar behavior, but in all cases ( just my line of work) the systems were in bad environmental places with heat issues and high particulate matter and the drives were not high quality, long in the tooth, and nearly full. I was never sure what to blame hardware failure, or software corruption.

Reply Parent Score: 3

Undomiel Member since:
2007-11-23

So far I have seen this happen once on a DAS attached to a 2003 server. One user kept calling in for a couple days about files disappearing and reappearing. The help desk and admins were scratching their heads a bit but didn't think too much of it. Then the file system just crapped out entirely and we had to restore the entire volume from backups.

Reply Parent Score: 2

darknexus Member since:
2008-07-15

Was I just lucky? *knocks on wood*

Probably not. I've seen three cases of this, total. Once on XP, twice on 7. It's not a common problem, but it is one that I've *never* had with *any* other filesystem and means I'm disinclined to trust NTFS as much as others do. It may not be common, but it can be quite nasty if you happen to see it. I've never figured out the exact chain of events to cause it; if I had, I'd have reported it for whatever good that would have done.

Reply Parent Score: 2