> I believe the above depends on the kernel version. My reading tells me that
> as of kernel 2.6.33
> write barriers are implemented correctly in which case, could I assume that
> it would be safe to use LVM?
If the write barriers are honored, LVM should be safe to use, inthe context of
VM’s at least. However one must also ensure thatthe filesystem honors them
as well. On physical systems, addi-tional requirements will apply.
Also, as others have said, slicing up / into separate filesystemsis something
we did in the ’80’s and the ’90’s of the past centu-ry on Solaris.
Barring availability of ZFS, having a single "whole disk /" isthe most
efficient use of disk storage capacity, and is adequateunless one is dealing
with massive amounts of storage, which iswhere /var/opt on additional
filesystems comes into play.
If systems are running the risk of filling filesystems to capaci-ty, then the
problem is architectural, not administrative; oneshould look into why this is
happening, and implement appropriatemeasures. For example, one system with a
filesystem full shouldnever be able to affect any application from functioning;
if itdoes, it is time to redesign the application, or send the vendorback to
the drawing board until the application is resilientenough to be able
to withstand random nodes going down for anyreason. A lot of the time, "rolling
up one’s own sleeves" is theapproach called for.
I have also seen /var split into its own separate filesystem in alot of places,
under the false logic that that action will pre-vent the system from
choking up, but the fact is, if /var isfull, the system will come to a
grinding halt. Also, "classic"filesystems, where this is most prevalent,
provide -m switch forminimum reserved space, where only root can write, thus
prevent-ing applications for bringing the system to a halt, so the
entireargument of separate filesystems is a straw man. Separate /,/usr,
/var, and /tmp filesystems do not prevent the system fromgrinding to a halt if
any part of that system misbehaves.
-------------------------------------------
smartos-discuss
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