Hi,
I revised my idea and thought about RAID 1+0 for some partitions, since there are 4 drives. This outline below might clarify what I was trying to mention earlier. Is this a feasible set-up that would be bootable (kernel compiled-in md, I'm no stranger to compiling kernels)? I'm interested to hear comments/opinions since I've never done this before. Like I said, it'll be running on a Dual-pentium pro 200 (W6-LI) machine, I have no idea if machines of that vintage have the 'cojones' for software raid or not.
My ideas of RAID1+0 / RAID5 disk system partitions MB /dev/hde 60GB 57241 (from controller) /dev/hdf 60GB 57241 (from controller) /dev/hdg 60GB 57241 (from controller) /dev/hdh 80GB 78125 (unconfirmed) /dev/hd* = applies to all drives considered here Device MB Type GB Mountpoint MD device RAIDed size (MB) GB /dev/hd*1 20 RAID1 + 0 0.02 /boot /dev/md1 40 0.04 /dev/hd*2 192 RAID1 + 0 0.19 Swap /dev/md2 384 0.38 /dev/hd*5 2048 RAID1 + 0 2 / /dev/md5 4096 4 /dev/hd*6 2048 RAID5 2 /home /dev/md6 6144 6 /dev/hd*7 52933 RAID5 51.69 /data /dev/md7 158799 155.08
Does swap being raided make sense? I hear that sometimes it's a good idea since a disk failure won't make you crash and then I heard elsewhere that it doesn't matter and the kernel automatically raids swap partitions anyway. I prepared the above in a spreadsheet btw so I could work out partition sizes.
Thanks in advance again for any comments.
Derek
On Tue, 11 Jan 2005 13:47:20 -0500, Derek Piper <derek.piper@xxxxxxxxx> wrote:
Hi,
I am new to RAID / md devices, although I've used Linux for a number of years. I decided it was high-time I had a RAID at home for important things (email, web-sites, son's baby pics, mp3s etc.). I happen to have a 3 Seagate 60GB hds and 1 80GB Seagate hd that I am considering using for a RAID.
My question is this, is it possible (and even a good idea) to use all 4 hard drives as members of a 4 x 60GB RAID5 array by leaving 20GB of the 80GB drive as a non-raided partition? I'll be using a Promise Ultra TX2/100 controller.
i.e.
hde -> 60 hdf -> 60 hdg -> 60 hdh -> 60/20
I heard about RAID6 too, though I'm assuming that will use up another disk's worth of disk space too.
i.e. RAID5 = 180GB usable size,wherease RAID6 = 120GB .. am I correct in my thinking?
I know many of you use far larger hard drives, I'm just trying to use the components I already had spare from a number of machines and reorganize to a RAID-backed fileserver.
The machine is a dual pentium-pro 200 (320MB RAM) .. would that be a dumb idea to use RAID5 on it because of the parity calculations needed?
Further to that, would it be a smarter idea to use RAID1 on all 4 of some small partition(s) at the start of the disks to house boot/root/usr partitions, and only RAID5 on a larger 'data' area of the drive that is more likely to be read than written to?
Derek,
I have a machine with 6 x 250GB SATA disks, but the configuration I use would work just as well for you. Here's what I'd do:
Partition all your drives the same.
Create one small partition of 1GB, plus one large partition using up the rest of the disk (i.e. around 59GB), *except* the 80GB drive. On this, create a 1GB partition, a 59GB partition, plus a third partition using up the rest of the disk (i.e. around 20GB)
Assuming these drives are /dev/hd[efgh], configure them as follows:
/dev/hd[ef]1 /dev/md0 / /dev/hd[gh]1 /dev/md1 swap /dev/hd[efgh]2 /dev/md2 lvm volume group /dev/hdh3 - use for whatever you want!
Now, use lvm to create logical volumes in your large volume group. I have created /var, /use, and use the rest for /home.
These are my arrays:
[root@dude slimserver]# mdadm --detail --scan
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=be8ad31a:f13b6f4b:c39732fc:c84f32a8
devices=/dev/sdb1,/dev/sde1
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=826170e2:cdd598d4:d212c9b1:6602deef
devices=/dev/sdc1,/dev/sdf1
ARRAY /dev/md5 level=raid5 num-devices=5 spares=1 UUID=a4bbcd09:5e178c5b:3bf8bd45:8c31d2a1
devices=/dev/sda2,/dev/sdb2,/dev/sdc2,/dev/sdd2,/dev/sde2,/dev/sdf2
ARRAY /dev/md0 level=raid1 num-devices=2 UUID=4b28338c:bf08d0bc:bb2899fc:e7f35eae
devices=/dev/sda1,/dev/sdd1
These are the lvm logical volumes:
[root@dude slimserver]# lvdisplay --- Logical volume --- LV Name /dev/audio_vg/usr_lv VG Name audio_vg LV UUID qseH0A-wKgo-xhB5-2tJ4-Qnxx-VOML-0eb43m LV Write Access read/write LV Status available # open 1 LV Size 10.00 GB Current LE 160 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:0
--- Logical volume --- LV Name /dev/audio_vg/var_lv VG Name audio_vg LV UUID nzH8uf-LhyU-o5My-tK48-ckaw-xzfL-esbfj4 LV Write Access read/write LV Status available # open 1 LV Size 5.00 GB Current LE 80 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:1
--- Logical volume --- LV Name /dev/audio_vg/home_lv VG Name audio_vg LV UUID zbixtc-S6mb-MTVR-WXGw-dkjG-EU9q-WeZItv LV Write Access read/write LV Status available # open 1 LV Size 914.38 GB Current LE 14630 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:2
This is what my filesystems look like:
[root@dude slimserver]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md0 1.4G 357M 985M 27% /
/dev/mapper/audio_vg-var_lv
5.0G 1.4G 3.3G 30% /var
/dev/mapper/audio_vg-usr_lv
9.9G 2.4G 7.0G 26% /usr
/dev/mapper/audio_vg-home_lv
915G 142G 764G 16% /homeAnd finally swap:
[root@dude slimserver]# swapon -s
Filename Type Size Used Priority
/dev/md1 partition 1469816 224 -1
R. -- http://robinbowes.com
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