[linux-lvm] Software raid on top of lvm logical volume
serrs at theserrs.net
Mon Nov 1 06:46:00 UTC 2004
I've done something like Markus explained. I had this email ready to go
a couple days ago, but the compose window was hidden for a while... I
hope it's not too stale for the original poster of this thread:
2.4.26 with latest LVM2 works well. I did something crazy, alot of
people probably don't understand why.
I have software RAID5.
md0 = hda5 hdb5 hdc5 hdd5 hde5
md1 = hda6 hdb6 hdc6 hdd6 hde6
md2 = hda7 hdb7 hdc7 hdd7
md3 = hda8 hdb8 hdc8 hdd8
Then I have just one big vgdata and one lvdata.
Why would I want to do this? I couldn't find any other way to have
redundancy and be flexible. If I replace a physical disk with a larger
one, for instance hde needs to be bigger so I can make md2 and md3
stretch across that disk too... then I am able to do pvmove from md2 to
a scratch disk, recreate md2 across hda7-hde7, then pvmove back.
Markus Baertschi wrote:
> Michael T. Babcock wrote:
>> I've thought about this numerous times -- there is the distinct
>> resizing advantage. Namely, if I create a software RAID partition, I
>> can't resize it afterward without destroying it. I have for example,
>> on occasion, had three disks set up where 1/3 of each was devoted to
>> a RAID-0 very fast striping set for data transfers that had to be
>> fast but if they were lost it wasn't critical, and 2/3 was set up as
>> RAID-5 for reliability of another set of data.
>> I understand this may not be optimal in some situations, but some of
>> us don't have thousands of dollars for SCSI HW RAID controllers.
> You can make life easier by creating several raid arrays on the same
> disks and tie them together with LVM.
> For example split your three 160GB drives into 4 partitions each and
> create a raid over the three disks.
> sda -> sda1+sda2+sda3+sda4, etc.
> md0 = sda1+sdb1+sdc1, md1=sda2+sdb2+sdc2, etc.
More information about the linux-lvm