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Old 09-11-2006, 10:17 AM   #1
shorun
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Question adding drives to an existing software mirror


i got a running ftp server, with 250GB mirror and a 300 GB mirror. now my 300 GB drive is full and i can't add new drives, so the 250GB needs to give up some room. it's no problem clearing these drives, but then i need to add the drives to the 300 GB mirror without losing any of the data on those drives.

any way can i just change the mirror to raid5 or maybe get the 2 mirrors to work in raid1 without losing the data?


just for the info, here's the current layout:
300+300 mirror
250+250 mirror

could it be possible to add these two mirrors together in eg:
300+300 \
................> new raid1
250+250 /

*edit to many typo's

Last edited by shorun; 09-11-2006 at 10:19 AM.
 
Old 09-11-2006, 10:44 AM   #2
MensaWater
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I'm assuming from your question that you want to have everything in one filesystem? (If not then why not just make the 2 different RAID 1 devices separate mounts?)

You can't really add dissimilar sized drives into a RAID 1. If you did RAID 5 (at the drive level) you could only go to the size of the smallest volumes (thereby losing 50 GB on each of your 300 GB drives). Of course this would gain you some space back because instead of giving up 300 GB and 250 GB for mirroring you'd only give up 350 GB total for RAID 5 (the 100 GB on your two 300 GB drives and 250 GB for parity).

Of course you can do RAID 5 at the partition level but that doesn't help if you're looking for a single filesystem.

Is this software RAID or hardware RAID? If it were me I'd probably just put both RAID 1s into Logical Volume Manager (LVM) in single Volume Group (VG) since it wouldn't care about disk sizes. I'd then make a single Logical Volume (LV) out of the VG to use as the mount point.

However I don't know how you could do that without losing the data. You'd need to do a full backup of the RAID 1s then the creations then restore the resulting mount.

"man lvm" will give you more info on the use of LVM.
 
Old 09-14-2006, 09:47 PM   #3
shorun
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thnx for the reply. i figured i could not do that. but then again, linux keeps amazing me with things i figured where impossible.

i'll be sure to check lvm, i've seen it before but it never came to me to use it. in the mean time the search for a 300 GB temp. storage drive has begun. it's either that or going to store for a ****load on dvd disks...

thnx anyway
 
Old 09-15-2006, 08:21 AM   #4
MensaWater
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I did say I'd put both RAID 1s in a single VG but that isn't required unless you need one filesystem. If you can live with more than one filesystem you could just partition the second RAID 1 or put in LVM and make LVs out of it.
 
  


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