Slow resilvering with mirrored ZIL

[Jeremy Chadwick]

On Wed, Jul 03, 2013 at 05:12:17PM +0200, mxb wrote:
> 
> Not sure if new are 4k. Done nothing about that.
> But the SECOND drive, resilvering is SLOW. Not the first one.
> 
> As stated below. Those changes are introduced to the system.
> ALL new driver ARE identical, except S/N of cause :)
> 
> On 3 jul 2013, at 16:55, Steven Hartland <killing at multiplay.co.uk> wrote:
> 
> > 
> > ----- Original Message ----- From: "Daniel Kalchev" <daniel at digsys.bg>
> > To: "mxb" <mxb at alumni.chalmers.se>
> > Cc: <freebsd-fs at freebsd.org>
> > Sent: Wednesday, July 03, 2013 3:40 PM
> > Subject: Re: Slow resilvering with mirrored ZIL
> > 
> > 
> >> On 03.07.13 16:36, mxb wrote:
> >>> Well, then my question persists - why I get so significant drop of speed while resilvering second drive.
> >>> The only changes to the system are:
> >>> 
> >>> 1. Second partition for ZIL to create a mirror
> >>> 2. New disks are 7200rpm. old ones are 5400rpm.
> >>> 
> > 
> > Its not something like the old disks are 512byte sectors
> > where as the new ones are 4k?
> > 
> > It this is the case having already replaced one disk you've
> > killed performance as its having to do lots more work reading
> > none 4k aligned data?

Not enough hard information to diagnose.  What's needed is below; you
can XXX out system names if you want, but please do not XXX out anything
else.

- Output from: dmesg

- Output from: zpool status

- Output from: zpool get all

- Output from: zfs get all

- Output from: "gpart show -p" for every disk on the system

- Output from: cat /etc/sysctl.conf

- Output from: cat /boot/loader.conf

- Output from: "smartctl -a" for every disk that's used by ZFS
  (please use smartmontools 6.1 or newer in this case; install
  ports/sysutils/smartmontools)

I can think of one tunable related to resilvering that may/might help
with your problem, but I'm not going to mention it until the above can
be provided.

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Making life hard for others since 1977.             PGP 4BD6C0CB |