ZFS: alignment/boundary for partition type freebsd-zfs

O. Hartmann ohartmann at walstatt.org
Tue Dec 26 16:25:36 UTC 2017


Running recent CURRENT on most of our lab's boxes, I was in need to replace and restore a
ZFS RAIDZ pool. Doing so, I was in need to partition the disks I was about to replace.
Well, the drives in question are 4k block size drives with 512b emulation - as most of
them today. I've created the only and sole partiton on each 4 TB drive via the command
sequence

gpart create -s GPT adaX
gpart add -t freebsd-zfs -a 4k -l nameXX adaX

After doing this on all drives I was about to replace, something drove me to check on
the net and I found a lot of websites giving "advices", how to prepare large, modern
drives for ZFS. I think the GNOP trick is not necessary any more, but many blogs
recommend to perform

gpart add -t freebsd-zfs -b 1m -a 4k -l nameXX adaX

to put the partition boundary at the 1 Megabytes boundary. I didn't do that. My
partitions all start now at block 40.

My question is: will this have severe performance consequences or is that negligible?

Since most of those websites I found via "zfs freebsd alignement" are from years ago, I'm
a bit confused now an consideration performing all this days-taking resilvering process
let me loose some more hair as the usual "fallout" ...

Thanks in advance,

Oliver

-- 
O. Hartmann

Ich widerspreche der Nutzung oder Übermittlung meiner Daten für
Werbezwecke oder für die Markt- oder Meinungsforschung (§ 28 Abs. 4 BDSG).
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