[linux-lvm] can I freeze I/O for some time to a given disk / md / dm device?

Tomasz Chmielewski mangoo at wpkg.org
Tue Dec 16 12:01:27 UTC 2008

Is it possible to "freeze I/O" for some time to a given disk / md / dm 

Say, "freeze I/O" so that userspace waits for any response for 30, 60 
seconds or more?

If not, is it possible to reset a link repeatedly, like ATA does when it 
hits certain disk problems? I.e., can I do the below manually?

ata4.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2 frozen
ata4.00: cmd 25/00:08:b8:c2:78/00:00:21:00:00/e0 tag 0 dma 4096 in
          res 40/00:00:bb:c2:78/40:00:21:00:00/e0 Emask 0x4 (timeout)
ata4.00: status: { DRDY }
ata4: hard resetting link

I need this to trace a problem with a userspace application which 
segfaults when ATA resets the link repeatedly (i.e. one broken drive in 
a RAID array).

Tomasz Chmielewski

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