unknown
1970-01-01 00:00:00 UTC
However, in dm.c there's the dm_blk_ioctl function which says the
following:
/* We only support devices that have a single target */
if (dm_table_get_num_targets(map) != 1)
goto out;
Intuitively it looks like this could prevent a raid1 target from working
as it apparently consists of rmeta and rimage subcomponents, but I
couldn't determine for certain if my intuition is correct. I did some
testing, and discards work just fine on a linear volume spanning two
different partitions, while they fail on a "RAID" mirror of two similar
partitions. Clearly, two devices in a mapping are not a problem.
- use one volume manager instead of two
- LVM is better suited to creating devices of varying sizes - leaving spare capacity for snapshots, etc
- no trim support with RAID through LVM (although, I'm not sure of the state in MD)
- no reshaping (changing from one RAID type to another) capability in LVM RAID.
brassow
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following:
/* We only support devices that have a single target */
if (dm_table_get_num_targets(map) != 1)
goto out;
Intuitively it looks like this could prevent a raid1 target from working
as it apparently consists of rmeta and rimage subcomponents, but I
couldn't determine for certain if my intuition is correct. I did some
testing, and discards work just fine on a linear volume spanning two
different partitions, while they fail on a "RAID" mirror of two similar
partitions. Clearly, two devices in a mapping are not a problem.
As an aside, can anyone point me to documentation or other resources
about the pros and cons of LVM native RAID1 setup (which I understand
uses MD RAID internally?) vs. MD RAID PV + LVM. It seems I might be able
to save some SSD space and only mirror the LVs I actually need to keep
safe from crashes.
I don't know if there is a specific list to point to out there, but I can give you a couple pros/cons.about the pros and cons of LVM native RAID1 setup (which I understand
uses MD RAID internally?) vs. MD RAID PV + LVM. It seems I might be able
to save some SSD space and only mirror the LVs I actually need to keep
safe from crashes.
- use one volume manager instead of two
- LVM is better suited to creating devices of varying sizes - leaving spare capacity for snapshots, etc
- no trim support with RAID through LVM (although, I'm not sure of the state in MD)
- no reshaping (changing from one RAID type to another) capability in LVM RAID.
brassow
_______________________________________________
linux-lvm mailing list
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/