[GTALUG] RAID and IX-2-dl
Lennart Sorensen
lsorense at csclub.uwaterloo.ca
Fri Feb 20 19:28:33 UTC 2015
On Thu, Feb 19, 2015 at 04:56:12PM -0500, D. Hugh Redelmeier wrote:
> I just bought a LenovoEMC / IOmega IX2-dl NAS box (cheap, of
> course). It has a pair of WD Green 2T disk drives.
>
> The supplied firmware is Linux, of course. With a pretty face.
>
> /proc/cpuid says "Feroceon 88FR131 rev 1 (v5l)" which I think is an
> unfortunately old ARM family. It has 256M of RAM. The kernel is
> "2.6.31.8".
>
> It offers me RAID 1, RAID 0, and "none". I don't think that I want
> either RAID and I'm not sure what "none" is.
>
> I don't want RAID 1 because It doesn't give me much reliability
> improvement for the price (halving the space) and it doesn't give me any
> speed improvement.
>
> I don't want RAID 0 since it gives me less reliability than no RAID.
>
> I want two different filesystems so that when one goes south, the other
> isn't lost.
I suspect none in fact means make each disk seperate. But it might not.
It could be that they mean:
RAID1: Mirror two identical disks
RAID0: Stripe data across two identical disks for speed
none: Concat the disks into one large disk, without added safety or
speed gains.
> Any advice on how to lightly prod this system to do what I want?
>
> Here's some configuration information.
>
> /etc/fstab doesn't mention the hard drives
>
> First, here's how it looks with the RAID1 setup.
>
> lsblk(8) says. (This command is new to me. I think that I like it):
>
>
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
> loop0 7:0 0 680.4M 1 loop /mnt/apps
> loop1 7:1 0 8M 0 loop /mnt/etc
> loop2 7:2 0 100K 0 loop /oem
> sda 8:0 0 1.8T 0 disk
> ├─sda1 8:1 0 20G 0 part
> │ └─md0 9:0 0 20G 0 raid1
> │ ├─md0_vg-BFDlv (dm-0) 253:0 0 4G 0 lvm /boot
> │ └─md0_vg-vol1 (dm-1) 253:1 0 16G 0 lvm /mnt/system
> └─sda2 8:2 0 1.8T 0 part
> └─md1 9:1 0 1.8T 0 raid1
> └─6366c931_vg-lv163c50af (dm-2) 253:2 0 1.8T 0 lvm /mnt/pools/A/A0
> sdb 8:16 0 1.8T 0 disk
> ├─sdb1 8:17 0 20G 0 part
> │ └─md0 9:0 0 20G 0 raid1
> │ ├─md0_vg-BFDlv (dm-0) 253:0 0 4G 0 lvm /boot
> │ └─md0_vg-vol1 (dm-1) 253:1 0 16G 0 lvm /mnt/system
> └─sdb2 8:18 0 1.8T 0 part
> └─md1 9:1 0 1.8T 0 raid1
> └─6366c931_vg-lv163c50af (dm-2) 253:2 0 1.8T 0 lvm /mnt/pools/A/A0
> mtdblock0 31:0 0 504K 0 disk
> mtdblock1 31:1 0 4K 0 disk
> mtdblock2 31:2 0 4K 0 disk
>
> df(1) says:
>
> Filesystem 1K-blocks Used Available Use% Mounted on
> rootfs 51200 4216 46984 9% /
> /dev/root.old 11339 3185 8154 29% /initrd
> none 51200 4216 46984 9% /
> /dev/md0_vg/BFDlv 4128448 714776 3203960 19% /boot
> /dev/loop0 691776 619873 71903 90% /mnt/apps
> /dev/loop1 7657 1010 6238 14% /mnt/etc
> none 7657 1010 6238 14% /etc
> /dev/loop2 128 128 0 100% /oem
> tmpfs 24776 80 24696 1% /run
> tmpfs 5120 4 5116 1% /run/lock
> tmpfs 49540 0 49540 0% /run/shm
> /dev/mapper/md0_vg-vol1 16493480 975280 15350636 6% /mnt/system
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /mnt/pools/A/A0
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/Backups
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/Documents
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/Movies
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/Music
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/SharedMedia
> /dev/mapper/6366c931_vg-lv163c50af 1902053516 202188 1901851328 1% /nfs/Pictures
>
> After I switched from RAID1 to "none":
>
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
> loop0 7:0 0 680.4M 1 loop /mnt/apps
> loop1 7:1 0 8M 0 loop /mnt/etc
> loop2 7:2 0 100K 0 loop /oem
> sda 8:0 0 1.8T 0 disk
> ├─sda1 8:1 0 20G 0 part
> │ └─md0 9:0 0 20G 0 raid1
> │ ├─md0_vg-BFDlv (dm-0) 253:0 0 4G 0 lvm /boot
> │ └─md0_vg-vol1 (dm-1) 253:1 0 16G 0 lvm /mnt/system
> └─sda2 8:2 0 1.8T 0 part
> └─md1 9:1 0 3.6T 0 linear
> └─529a853a_vg-lv1ac0e3be (dm-2) 253:2 0 3.6T 0 lvm /mnt/pools/A/A0
> sdb 8:16 0 1.8T 0 disk
> ├─sdb2 8:18 0 1.8T 0 part
> │ └─md1 9:1 0 3.6T 0 linear
> │ └─529a853a_vg-lv1ac0e3be (dm-2) 253:2 0 3.6T 0 lvm /mnt/pools/A/A0
> └─sdb1 8:17 0 20G 0 part
> └─md0 9:0 0 20G 0 raid1
> ├─md0_vg-BFDlv (dm-0) 253:0 0 4G 0 lvm /boot
> └─md0_vg-vol1 (dm-1) 253:1 0 16G 0 lvm /mnt/system
> mtdblock0 31:0 0 504K 0 disk
> mtdblock1 31:1 0 4K 0 disk
> mtdblock2 31:2 0 4K 0 disk
That does in fact look like with none as the setting, it is just adding
each disk to the volumegroup for the pool.
It would seem with this design, the only option that will tolerate
disk failures is RAID1. The others will have complete data loss if any
disk fails. RAID0 gives extra speed but requires identical disks,
while none does not give extra speed and allows different disk sizes to
be in use.
--
Len Sorensen
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