[CentOS] XFS and LVM2 (possibly in the scenario of snapshots)

Mathieu Baudier mbaudier at argeo.org
Thu Dec 10 15:26:15 UTC 2009

> LVM like md raid and drbd is a layered block device and
> If you turn the wire caches off on the HDs then there is no problem,
> but HDs aren't designed to perform to spec with the write cache
> disabled they expect important data is written with FUA access (forced
> unit access), so performance will be terrible.

I hope that I'm not going too much off topic here, but I'm getting
worried not to be sure to understand, especially when it has to do
with data safety:

Considering a stack of:
- ext3
- on top of LVM2
- on top of software RAID1
- on top of regular SATA disks (no hardware RAID)
is it "safe" to have the HD cache enabled?

(Note: ext3, not XFS, hence the possible off-topic...)

In other words, is this discussion about barriers, etc. only relevant to XFS?

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