[zfs-discuss] raid10 vs raid-z2?

Dan Swartzendruber dswartz at druber.com
Wed May 29 13:31:14 EDT 2013

A couple of things: I use raid10 for my pool, but it's mostly a vsphere
datastore repository, so random read performance is important.  For your
case, how much random read do you expect?  You say there are home
directories, but how much traffic do those take?  For your use case,
raidz2 does sound safer, although if you have backups, I'd not worry
overmuch about losing both sides of a mirror.  Raidz2 would have the
advantage of not only being safer, but having 4 disks of usable space, as
opposed to 3.  L2ARC (SSD cache) will be mostly useless for the media, but
maybe not so much for the home directories.  I'd rather not see you try to
economize by splitting up the SSD, especially since that would require you
to put the root filesystem on the SSD, which I don't think is really ready
for primetime yet.  The trick here is to set primarycache=none and
secondarycache=none for the dataset(s) holding the (mostly) readonly media
files, so as not to waste ARC and L2ARC on that.

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