Re: RAID and/or LVM suggestions?
Quoting Chris Boot <bootc@bootc.net>:
Hi all,
I know this isn't strictly Debian related, but I'll be implementing
this on a Sarge system so I thought it appropriate.
I've just taken the plunge and bought 4 250GB SATA hard drives and am
planning on implementing a RAID, with LVM2 layered over the top of
that. The main purpose of this system will be to store films, music,
and other general fileserver uses: in other words larger files as
opposed to smaller ones. I've had a few ideas about how to set it all
up, but I'm wondering what others would suggest...
Option 1: RAID 10
md0: RAID 1 (sda sdc)
md1: RAID 1 (sdb sdd)
md2: RAID 0 (md0 md1)
Option 2: RAID 0+1
md0: RAID 0 (sda sdc)
md1: RAID 0 (sdb sdd)
md2: RAID 1 (md0 md1)
Option 3: RAID 5
md0: RAID 5 (sda sdb sdc sdd)
Option 4: 2xRAID 0 + LVM striping
md0: RAID 0 (sda sdc)
md1: RAID 0 (sdb sdd)
Striping would be implemented through LVM.
In particular I'm having trouble figuring out what the actual
performance / fault-tolerance differences between RAID 10 and RAID 0
+1 might be. I hear RAID 5 is hardly worth using in software, and I'm
not sure I'd be using it properly with only 4 drives. As for the
final option, would there be any advantage at all to using this
method (bearing in mind I'll be using LVM in any case)? Would anyone
have any other suggestions?
Hello,
If I had a similar setup, I would be considering option 1 or option 3.
Option 4 doesn't give any fault tolerance. If a drive dies, you'll be
quickly restoring from backup.
Option 3 with Raid 5 would give you more overall disk space and might
have quicker reads than option 1 (3 disks striped compared to just 2).
But I get the feeling that RAID 10 is the new thing these days if you
have enough hard disks.
I'm in the process of converting my SW raid 5 to raid 10. The rebuild
times of RAID 5 just take too long for our environment if a disk were
to fail.
In case you haven't seen it already, check out
http://miracleas.com/BAARF/BAARF2.html
If you have the time, I would suggest setting up your arrays, and run
some tests. (iozone, and bonnie can be installed and used for
benchmarking)
or just perform some every day tasks, and get a feel for how it runs.
Then, change it to match your other options, and test it again.
See which one works best for you.
Cheers,
Mike
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