Messages in this thread | | | Date | Wed, 3 Dec 2008 19:33:56 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: writing file to disk: not as easy as it looks |
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On Wed, 3 Dec 2008, Pavel Machek wrote:
> > > CRC errors, lost IRQs and the like are retried by the midlayer and > > > drivers and the error handling strategies will also try things like > > > reducing link speeds on repeated CRC errors. > > > > I meant for example loose cable or so --- does it make sense to retry > > indefinitely (until the admin plugs the cable or unmounts the filesystem) > > or return error to the filesystem after few retries? > > It is quite non-trivial to detect if it is "disk plugged back in" > vs. "faulty disk unplugged, new one plugged in"... so I suppose > automatic retry after failure of connection to disk is quite hard to > get right.
Unless the SATA controller has the plug interrupt (very few have), there is no way for the kernel to detect that an old SATA disk was unplugged and a new one was plugged in.
So the answer is that the admin must not hot-swap disk unless unmounting the filesystem or notifying the RAID layer about it. If you hot-swap softraid1/4/5 disk, you definitely damage data, because the softraid layer has no way to find out about the hotswap.
Mikulas
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