TRIM, iSCSI and %busy waves

Steven Hartland killing at
Thu Apr 5 14:57:46 UTC 2018

You can indeed tune things here are the relevant sysctls:
sysctl -a | grep trim |grep -v kstat
vfs.zfs.trim.max_interval: 1
vfs.zfs.trim.timeout: 30
vfs.zfs.trim.txg_delay: 32
vfs.zfs.trim.enabled: 1
vfs.zfs.vdev.trim_max_pending: 10000
vfs.zfs.vdev.trim_max_active: 64
vfs.zfs.vdev.trim_min_active: 1
vfs.zfs.vdev.trim_on_init: 1


On 05/04/2018 15:08, Eugene M. Zheganin wrote:
> Hi,
> I have a production iSCSI system (on zfs of course) with 15 ssd disks 
> and it's often suffering from TRIMs.
> Well, I know what TRIM is for, and I know it's a good thing, but 
> sometimes (actually often) I'm seeing my disks in gstat are 
> overwhelmed by the TRIM waves, this looks like a "wave" of 20K 
> 100%busy delete operations starting on first pool disk, then reaching 
> second, then third,... - at the time it reaches the 15th disk the 
> first one if freed from TRIM operations, and in 20-40 seconds this 
> wave begins again.
> I'm also having a couple of iSCSI issues that I'm dealing through 
> bounty with, so may be this is related somehow. Or may be not. Due to 
> some issues in iSCSI stack my system sometimes reboots, and then these 
> "waves" are stopped for some time.
> So, my question is - can I fine-tune TRIM operations ? So they don't 
> consume the whole disk at 100%. I see several sysctl oids, but they 
> aren't well-documented.
> P.S. This is 11.x, disks are Toshibas, and they are attached via LSI HBA.
> Thanks.
> Eugene.
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