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! =)

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]

Post by 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!
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.