[ILUG] Highpoint Sata RAID
weeboy at conorwynne.com
Sun Mar 27 13:58:23 IST 2005
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> Growing an array has been discussed on list before. the short answer is
> either use LVM (and not RAID - or RAID1) or forget it.
> Growing the
> filesystem is easy - growing a RAID5 / RAID6 array is not practical.
> RAID4 can be grown, but is generally not supported except on high-end
> storage systems (where you DO need to throw more disk in, grow a
> filesystem and carry on without down-time. See NetApp's WAFL for an
> example of this.)
> I'm open to correction on this, of course - and further developments
> may mean that what's impractical on Linux today becomes the 'done thing'
> tomorrow :-)
> Hope this helps.
> Best regards,
Actually you can and should use RAID.
e.g.: you have a RAID1, and you need to grow it.
Well simply create a new LUN with your shiny new drives (JBOD,
RAID1/2/3/4/5/10), then LVM across the two ARRAYS. This is what LVM was
designed for and it works very well.
Remember, RAID is simply for redundancy, the LUN is presented to the OS,
not the disks as such, therefore adding a new RAID array is exactly as
easy as adding a JBOD to an LVM volume.
Here is an example of this:
Personalities : [raid1]
read_ahead 1024 sectors
md0 : active raid1 sdb1 sda1
102144 blocks [2/2] [UU]
md1 : active raid1 sdb2 sda2
17680128 blocks [2/2] [UU]
md2 : active raid1 sdd1 sdc1
8883840 blocks [2/2] [UU]
Filesystem Size Used Avail Use% Mounted on
6.8G 4.1G 2.4G 64% /
/dev/md0 97M 24M 69M 26% /boot
5.3G 2.2G 2.8G 45% /home
none 502M 0 502M 0% /dev/shm
13G 1.5G 11G 13% /var
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