Slow resilvering with mirrored ZIL

[Daniel Kalchev]

On 05.07.2013, at 17:53, Jeremy Chadwick <jdc at koitsu.org> wrote:

> On Fri, Jul 05, 2013 at 01:37:58PM +0300, Daniel Kalchev wrote:
>> 
>> On 05.07.13 02:28, Steven Hartland wrote:
>>> 
>>> 
>>> If anyone wants my current patches which add switch to 4k ashift
>>> by default
>>> as a sysctl + works with QUIRKS too, just let me know.
>>> 
>>> They are well tested, just we want more options before putting in
>>> the tree.
>> 
>> Is it not easier to add this as an option to zpool create, instead
>> of an sysctl?
>> 
>> That is, I believe we have two scenarios here:
>> 
>> 1. Having an sysctl that instructs ZFS to look at the FreeBSD quirks
>> to decide what the ashift should be, instead of only querying the
>> 'sectorsize' property of the storage. I believe we might not even
>> need an sysctl here, just make it default to obey the quirks --- but
>> sysctl for the interim period will not hurt (with the proper
>> default).
> 
> I can expand on this one (specifically "relying on sectorsize of the
> media"): no, this will not work reliably, for two reasons.  

This is how ZFS works now. While I  am we'll aware that most people use disks with all the quirks manufacturers put there, lets not forget ZFS was designed for the enterprise environment, where "storage device" has much wider meaning and "sector size" also varies wildly.

Having said this and because FreeBSD actually goes via geom for disks now, figuring out the correct "sector size" is for geom to do. As it is now, perhaps ZFS should be made to query the "stripe size" property of the geom provider and not the "sector size". A sysctl to that effect makes more sense to me, will make things more automatic for most users.

Daniel