Re: Kernel logging I/O Errors for Disk Images
Re: Kernel logging I/O Errors for Disk Images
- Subject: Re: Kernel logging I/O Errors for Disk Images
- From: Nick Blievers <email@hidden>
- Date: Tue, 06 Nov 2012 15:37:19 -0600
- Acceptlanguage: en-US
- Thread-topic: Kernel logging I/O Errors for Disk Images
Hi,
I can't answer all your questions, but can at least clarify some of it. Based on mount.h we can see what the events are:
#define VQ_VERYLOWDISK 0x0200 /* file system has *very* little disk space left */
#define VQ_LOWDISK 0x0004 /* we're low on space */
Which kind of makes sense, the disk image may not have very much free space, and this is probably generated on mount.
The errors however, I can't help with. Definitely seems odd,
Nick
On 06/11/2012, at 9:29 PM, Julian Mayer wrote:
> hello
>
> i need some more information about when and why the kernel logs "I/O Errors" to the kernel/system logfile for disk images.
>
> background:
> whenever a I/O operation fails, the kernel logs a I/O error looking like this:
> kernel[0]: disk0s2: I/O error.
> this is quite common for optical media, e.g. when they are scratched.
> when this occurs repeatedly normal harddisks this is often a sign of serious disk-problems (e.g. disk run out of bad blocks, defective cabling or controller, etc).
> therefore my app is able to recognice I/O errors that have been logged and warn the user about it.
>
> now, the weird thing is, i recently discovered that sometimes the kernel will also log I/O errors for disk images in addition to real devices as well. i believed this to be impossible because it makes no sense at all, after all a disk image is just a file stored on another volume.
>
> i'd like to have some more information about when and why this can occur (so i can know whether this is something my app should ignore or inform the user about), and what it means. does a I/O error occuring on a disk image mean the image is damaged? shouldn't it just fail to mount in this case? or does it mean there is a problem on the volume where the image is stored? but shouldn't the I/O error get logged for that volume then?
>
> thanks, julian
>
> p.s. the log-file entries indicating an I/O error occuring on a disk image that was forwarded to me from a customer and clearly indicates the error being logged for a mounted image:
>
>
> Oct 27 19:22:07 xxx.local diskarbitrationd[15]: unable to probe /dev/disk3 (status code 0xFFFFFFFC).
> Oct 27 19:22:07 --- last message repeated 1 time ---
> Oct 27 19:22:07 xxx kernel[0]: disk3: I/O error.
> Oct 27 19:22:09 --- last message repeated 1 time ---
> Oct 27 19:22:09 xxx.local KernelEventAgent[42]: tid 00000000 received event(s) VQ_LOWDISK, VQ_VERYLOWDISK (516)
> Oct 27 19:22:09 xxx.local KernelEventAgent[42]: tid 00000000 type 'hfs', mounted on '/private/tmp/.vbfolder_IdHqvC', from '/dev/disk3s2', low disk, very low disk
> Oct 27 19:35:16 xxx.local SMARTReporter[278]: I/O-Error check: ERROR! - Found 3 problems on 1 of 3 checked disk(s): I/O Error found on disk: /dev/disk3 Name: 'Lifetime Map Updater' Errors: 3
>
> p.s.s. what does the "low disk, very low disk" thing mean? ;)<smime.p7s> _______________________________________________
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