>>> 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). >> >> Yikes... >> >> Ok, shouldn't there be a tool or tools to help with this? Ie, boot up on a >> bootable tools disk on the system with all drives connected, then let it >> 'analyze' your system, maybe ask you some questions (ie, how you will be >> configuring the drives/RAID, etc), then spit out an optimized config for >> you? >> >> It is starting to sound like you need to be a dang engineer just to use >> ZFS... >> > > Just do ashift=12 and you're good to go. No need to analyze further. > > The reason I said that because in the future, *all* drives will have 4 > KiB sectors. Currently, many drives still have 512 B sectors. But when > one day your drive dies and you need to replace it, will you be able > to find a drive with 512 B sectors? > > Unlikely. > > That's why, even if your drives are currently of the 'classic' 512 B > ones, go with ashift=12 anyway. > > For SSDs, the situation is murkier. Many SSDs 'lie' about their actual > sector size, reporting to the OS that their sector size is 512 B (or 4 > KiB). No tool can pierce this veil of smokescreen. The only way is to > do research on the Internet.
OK, so figure out what SSD you're using and Google to find the correct ashift? - Grant
