[zfs-discuss] Re: disappearing zvols

Fajar A. Nugraha list at fajar.net
Fri Apr 20 01:45:13 EDT 2012


On Fri, Apr 20, 2012 at 11:20 AM, Darik Horn <dajhorn at vanadac.com> wrote:
> This seemed like an easy optimization, but no dice.  I tried to
> improve performance by putting the dataset name in a sysfs attribute
> on the zvol device.

> The current udev rule is slow at system start because it calls an
> external program for each node:

I wonder how much of the slowness-and-high-load is due to "external
program" on zfs part.

Since native udev rules (e.g. 60-persistent-storage.rules) also use
external program (scsi_id), I imagine udev developers had considered
using external program to be good enough. Then again, it might be part
of a flaw in default udev rules, which would cause "normal" linux
distros to be unsuitable to handle several hundred block devices, with
or without zfs.

> Unfortunately, the necessary Linux kernel infrastructure is restricted
> and cannot be used by the ZFS driver:
>
>        FATAL: modpost: GPL-incompatible module zfs.ko uses GPL-only symbol
> 'device_create_file'

The gory, historical, details on why an external program was chosen:
https://github.com/zfsonlinux/zfs/issues/102

-- 
Fajar



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