On Thu, Sep 19, 2013 at 2:44 PM, Hinnerk van Bruinehsen <h.v.bruineh...@fu-berlin.de> wrote: > On Wed, Sep 18, 2013 at 09:49:40PM -0700, Grant wrote: >> > I think many folks are interested in upgrading to EXT4 with RAID from >> > an ordinary JBOD workstation(server); or better yet to ZFS on RAID. I wish >> > one of the brighter minds amongst us would put out a skeleton >> > (wiki) information page as such: >> > >> > http://wiki.gentoo.org/wiki/ZFS+RAID >> > >> > I know I have struggled with completing this sort of installation >> > several time in the last 6 months. I'm sure this (proposed) wiki page >> > would get lots of updates from the Gentoo user community. Surely, >> > I'm not qualified to do this, or it would have already been on the >> > gentoo wiki.... >> > >> > Much of the older X + RAID pages are deprecated, when one considers >> > the changes that accompany such an installation ( Grub2, UUID, fstab, >> > partitioning of drives, Kernel options, just to name a few). We're >> > talking about quite a bit of deviation from the standard handbook >> > installation, fraught with hidden, fatal mis-steps. >> >> Any important points or key concepts a ZFS newbie should remember when >> installing with it for the first time? >> >> - Grant > > > You should definitely determine the right value for ashift on pool creation > (it controls the alignment on the medium). It's an option that you afaik can > only set > on filesystem creation and therefore needs a restart from scratch if you get > it > wrong. > According to the illumos wiki it's possible to run a mixed pool (if you have > drives requiring different alignments[1]) > If in doubt: ask ryao (iirc given the right information he can tell you which > are the right options for you if you can't deduce it yourself). > Choosing the wrong alignment can cause severe performance loss (that's not > a ZFS issue but happened when 4k sector drives appeared and tools like fdisk > weren't aware of this). > > WKR > Hinnerk >
Especially with SSDs. One must find out the blocksize used by his/her SSDs. With spinning disks, setting ashift=12 is enough since no spinning disks have sectors larger than 2^12 bytes. With SSDs, one might have to set ashift=13 or even ashift=14. Rgds, -- FdS Pandu E Poluan ~ IT Optimizer ~ • LOPSA Member #15248 • Blog : http://pepoluan.tumblr.com • Linked-In : http://id.linkedin.com/in/pepoluan
