Re: ZFS raidz and 4k sector disks

[Alexey Tarasov]

Hello.

I see considerably increased performance when creating over gnop -S 4096 virtual disk. Even when I create zpool over raw disks the performance is very bad and concurent writes stalls. When using gnop, zfs works VERY fast!

Btw, here is another discussion, may be there is a bug in a mav@ commit, because he has added support for >512 sector size:
http://lists.freebsd.org/pipermail/freebsd-current/2010-April/016495.html

Превед Украине! =)

On 09.04.2010, at 12:28, Andriy Gapon wrote:

> on 08/04/2010 16:55 Alexey Tarasov said the following:
>> Hello.
>>
>> I've tried all methods and realized that unfortunately the only working
>> method is gnop. So you can't use these disks for ZFS at all now.
>
> Why? And what are you actually trying to do?
> My understanding was that even with 512-byte sectors ZFS still aligns its
> on-disk data with > 4K alignment.
> Do you see otherwise? What problem do you have?
>
> --
> Andriy Gapon

--
Alexey Tarasov

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[Andriy Gapon]

on 09/04/2010 14:14 Alexey Tarasov said the following:
> Hello.
>

> I see considerably increased performance when creating over gnop -S 4096 virtual disk. Even when I create zpool over raw disks the performance is very bad and concurent writes stalls. When using gnop, zfs works VERY fast!
>
> Btw, here is another discussion, may be there is a bug in a mav@ commit, because he has added support for >512 sector size:
> http://lists.freebsd.org/pipermail/freebsd-current/2010-April/016495.html

Looks like I was wrong:
/*
* Determine the device's minimum transfer size.
*/
*ashift = highbit(MAX(pp->sectorsize, SPA_MINBLOCKSIZE)) - 1;

This is in vdev_geom_open and SPA_MINBLOCKSIZE is 512.

--
Andriy Gapon