Hi Peter,
On 12/26/2014 04:35 PM, Peter Kieser wrote:
On 2014-12-23 9:24 AM, Goldwyn Rodrigues wrote:
This md device can be used as a regular shared device. There are no
restrictions on the type of filesystem or LVM you can use, as long as
you observe clustering rules of using a shared device.
This is very vague. I feel like this is a huge layering violation. LVM
or filesystem on top of mdadm should not have to be aware of what is
going on below.
How is this a layering violation? I said there are _no_ restrictions as
long you follow the clustering rules of using a shared device. This
device can be used as a regular device with the filesystem being unaware
of how the data is handled underneath. The only thing the md device
ensures is that the data (between mirrors) is consistent for the cluster.
By clustering rules I mean rules such as:
- Use a clustered filesystem
- Use cLVM (as opposed to usual LVM) on top of MD-RAID.
- Use local filesystems in active/passive mode
Otherwise, I feel like other clustered filesystems that
include RAID are better suited.
such as?
As it stands, what are the benefits of
using this over $CLUSTER_FS?
This is not a cluster filesystem. This is a RAID which is made cluster
aware for your shared storage. This provides redundancy at the device
level for a clustered filesystem. Your cluster shared storage is a
single point of failure (in case hardware-based raid is not used) and
this software-based solution avoids making it a single point of failure.
An example usage scenario (not limited to) could be using it across two
iSCSI devices to ensure higher availability.
--
Goldwyn
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