[clue] [tech] force Linux kernel to release swap device

Shawn Perry shawn at redmop.com
Thu Jul 28 11:35:02 MDT 2011


If you have a USB to SATA adapter, reconnect the old /dev/sdb and then try
swapoff.

Did you try swapoff /dev/sdb ?

Is there currently another /dev/sdb?


Shawn T Perry
Red Mop Computing Services
email: shawn at redmop.com
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On Thu, Jul 28, 2011 at 11:20 AM, Jim Ockers <ockers at ockers.net> wrote:

> **
> Hi CLUEbies,
>
> In a test of my sysadmin mojo I changed out all of the SATA hard drives in
> a server without downing the server or any of the VMs it was running.  I
> used Linux software RAID1 to move the data around to whatever drives were
> swapped in and that all worked perfectly fine.
>
> One thing I forgot to do, though, was release the swap space on /dev/sdb
> before pulling the drive.  The OS was not using any swap space before I
> pulled the drive, and it is still not using much/any swap space now.
> However, the /dev/sdb device is not freed and can't be re-used, and swapoff
> -a doesn't work, and now I see these sorts of messages in the system log:
>
> scsi 1:0:0:0: rejecting I/O to dead device
> Write-error on swap-device (8:16:1000)
> scsi 1:0:0:0: rejecting I/O to dead device
> Write-error on swap-device (8:16:392)
> Write-error on swap-device (8:16:400)
> Write-error on swap-device (8:16:408)
> scsi 1:0:0:0: rejecting I/O to dead device
> Write-error on swap-device (8:16:520)
>
> I guess /dev/sdb is 8,16.
>
> There is swap space available on /dev/sda now (I remembered to release that
> swap space before pulling the drive and replacing it), but it's just that
> there seems to be now way to get the kernel to release its swap usage on
> /dev/sdb, which doesn't exist any more as a device in the system.
>
> swapoff -a doesn't do it, nor does any other arguments to swapoff (like
> swapoff /dev/sdb2).
> eject /dev/sdb doesn't do it.
> echo "- - -" > /sys/class/scsi_host/host1/scan to force a SATA rescan also
> doesn't do it.
> The drive I put in the 2nd slot showed up as sde, so now I have in order:
> sda, sde, sdc, sdd.
>
> Any ideas for how I can force the kernel to release its swap space on the
> nonexistent drive, without a reboot of the host OS (which will also occasion
> a reboot of all the VMs?  Yes I know I should have done it BEFORE pulling
> the drive but I forgot, OK?
>
> Thanks,
> Jim
>
> --
> Jim Ockers, P.Eng. (ockers at ockers.net)
> Contact info: http://www.ockers.net/msi.html
>
>
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