[OpenIndiana-discuss] SSDs for OI hipster ZFS root mirror?

[Bob Friesenhahn]

The cost of atime is not very dramatic when using zfs except for 
perhaps the snapshots issue which was already mentioned.  This is 
because the atime updates are cached in memory and are only written to 
underlying store at the next zfs sync interval.  So maybe atime will 
be updated in the filesystem after 5 seconds, although a hundred 
thousand or a million accesses occured in the mean time.  It is pretty 
common that when one file in a directory has been accessed, that many 
files in that same directory have been accessed, so the number of 
actual writes is reduced.

Support of atime from a network client is more serious since 
supporting atime results in more network activity since the server 
needs to be informed of it.

Regardless, I turn off atime support in all zfs filesystems and 
network mounts where it is not needed.

It seems unlikely that atime is a serious factor when it comes to 
concerns about wearing out a flash device unless it is an extremely 
fragile device.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
Public Key,     http://www.simplesystems.org/users/bfriesen/public-key.txt