2012-04-17 5:15, Richard Elling wrote:
For the archives...
Write-back cache enablement is toxic for file systems that do not issue
cache flush commands, such as Solaris' UFS. In the early days of ZFS,
on Solaris 10 or before ZFS was bootable on OpenSolaris, it was not
> uncommon to have ZFS and UFS on the same system.
NB, there are a number of consumer-grade IDE/*ATA disks that ignore
disabling
the write buffer. Hence, it is not always a win to enable the write
buffer that cannot
be disabled.
-- richard
For the sake of archives, can you please post a common troubleshooting
techinque which users can try at home to see if their disks honour the
request or not? ;) I guess it would involve random-write bandwidths in
two cases?
And for the sake of archives, here's what I do on my home system for
its pools to toggle the cache on disks involved (could be scripted
better to detect disk names from zpool listing, but works-for-me
as-is):
# cat /etc/rc2.d/S95disable-pool-wcache
#!/bin/sh
case "$1" in
start)
for C in 7; do for T in 0 1 2 3 4 5; do
( echo cache; echo write; echo display; echo disable; echo
display ) | format -e -d c${C}t${T}d0 &
done; done
wait
sync
;;
stop)
for C in 7; do for T in 0 1 2 3 4 5; do
( echo cache; echo write; echo display; echo enable; echo
display ) | format -e -d c${C}t${T}d0 &
done; done
wait
sync
;;
*)
for C in 7; do for T in 0 1 2 3 4 5; do
( echo cache; echo write; echo display ) | format -e -d
c${C}t${T}d0 &
done; done
wait
sync
;;
esac
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