CentOS - Feb 2015 - CentOS 7: software RAID 5 array with 4 disks and no spares?

On 2/18/2015 8:20 PM, Chris Murphy wrote:
> On Wed, Feb 18, 2015 at 3:37 PM, Niki Kovacs<info at microlinux.fr> 
wrote:
>> >Le 18/02/2015 23:12, Chris Murphy a ?crit :
>>> >>
>>> >>"installer is organized around mount points" is
correct, and what gets
>>> >>mounted on mount points? Volumes, not partitions.
>> >
>> >
>> >Says who?
> Because it's ambiguous. A partition might entirely contain a volume (a
> filesystem), but in your case none of your partitions contain a
> volume. They're members of md raid first, only once that's
assembled
> is there a logical block device, which happens to contain the volume,
> and it is the volume you're mounting. All you have to do is check
> fstab, partitions aren't assigned mount points, volumes are.
and I make my mdraid's PV's for lvm, and create LV's that are my
file
systems which I mount.  so thats one MORE level of indirection.

disks -> partition(s) -> mdraid devices -> PVs -> VG -> LV ->
file
system.   phew.





-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast

On Wed, Feb 18, 2015 at 9:25 PM, John R Pierce <pierce at hogranch.com>
wrote:
> disks -> partition(s) -> mdraid devices -> PVs -> VG -> LV
-> file system.
> phew.
You might be a candidate for LVM integrated raid. It uses the md
kernel code on the backend, but it's all LVM tools to create, manage
and monitor. The raid level is defined per LV, instead of all LV's in
a VG inheriting the underlying raid. It supports all levels of raid
including 5/6.

It doesn't quite have all the features of mdadm. But the flexibility
it offers for use cases where LV's are often being created and
destroyed and different redundancy levels/types are desired, it's
neat.

And eventually, one of these years, Btrfs. That is so much simpler to
create and manage.

disk>no partition>Btrfsraid>subvolumes instead of partitions

It doesn't have all the features of mdadm or lvm, especially when it
comes to VM images. But for general purpose data, it's nice. It'll use
different sized drives in a raid56, no fuss, no having to tell it how
to do that. Online addition of yet another (unlike sized) drive and it
just starts using it with a single 'btrfs device add' command. No
restripe/resilver needed.

-- 
Chris Murphy

On 2/18/2015 9:39 PM, Chris Murphy wrote:
> You might be a candidate for LVM integrated raid. It uses the md
> kernel code on the backend, but it's all LVM tools to create, manage
> and monitor. The raid level is defined per LV, instead of all LV's in
> a VG inheriting the underlying raid. It supports all levels of raid
> including 5/6. ... ...
> ...
> ... ... btrfs ...
actually, I prefer zfs.   I was just saying how I do it on CentOS, where 
zfs is not really an option.

# zpool create zbig mirror hd10 hd11 mirror hd12 hd13 mirror hd14 hd15 
mirror hd16 hd17 mirror hd18 hd19 spare hd20 hd21
# zfs create -o mountpoint=/mystuff zbig/mystuff

done.

.... but, is that lvm integrated raid stuff available in RHEL/CentOS 6 
or 7 yet ?


-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast