On 29/11/2016 12:30, Eugene M. Zheganin wrote:
Hi.
On 28.11.2016 23:07, Steven Hartland wrote:
Check your gstat with -dp so you also see deletes, it may be that your
drives have a very slow TRIM.
Indeed, I see a bunch of delete operations, and when TRIM disabled my
engineers report that the performance is greatly increasing. Is this it ?
Yep sounds like the TRIM on the disk is particularly poor.
You can download, compile and run
http://blog.multiplay.co.uk/dropzone/freebsd/ioctl-delete.c
You can run with: ioctl-delete <device> <startblock> <blockcount>
This will time and give you performance info with regards to delete
requests.
It uses raw BIO_DELETE commands to the device so eliminates filesystem
latency (don't run on a device that's in use).
You'll likely want to put some data on there though as often FW
eliminates the delete if it will have no effect e.g.
dd if=/dev/random of=<device> bs=1m count=20480
Regards
Steve
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