add paragraph for IO Thread option

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

diff --git a/qm.adoc b/qm.adoc
index ab6d5bd53edf69c7cd10f792003e9f675b2c2e42..f6c968adc7931ef1dabbd4b7f4a398bbdcfb7b3a 100644 (file)
--- a/qm.adoc
+++ b/qm.adoc
@@ -162,6 +162,12 @@ when the filesystem of a VM marks blocks as unused after removing files, the
 emulated SCSI controller will relay this information to the storage, which will
 then shrink the disk image accordingly.
 
 emulated SCSI controller will relay this information to the storage, which will
 then shrink the disk image accordingly.
 

+The option *IO Thread* can only be enabled when using a disk with the *Virtio* controller,
+or with the *SCSI* controller, when the emulated controller type is *VIRTIO*.
+With this enabled, Qemu uses one thread per disk, instead of one thread for all,
+so it should increase performance when using multiple disks.
+Note that backups do not currently work with *IO Thread* enabled.
+

 Managing Virtual Machines with 'qm'
 ------------------------------------
 
 Managing Virtual Machines with 'qm'
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