Gentoo Archives: gentoo-user

From: Florian Philipp <lists@×××××××××××.net>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] dmraid, mdraid, lvm, btrfs, what?
Date: Tue, 29 Nov 2011 19:25:21
Message-Id: 4ED53120.2030209@binarywings.net
In Reply to: Re: [gentoo-user] dmraid, mdraid, lvm, btrfs, what? by Michael Mol
1 Am 29.11.2011 19:39, schrieb Michael Mol:
2 > On Tue, Nov 29, 2011 at 1:20 PM, Florian Philipp <lists@×××××××××××.net> wrote:
3 >> Am 29.11.2011 14:44, schrieb Michael Mol:
4 >>> On Tue, Nov 29, 2011 at 2:07 AM, Florian Philipp <lists@×××××××××××.net> wrote:
5 >>>> Am 29.11.2011 05:10, schrieb Michael Mol:
6 >>>>> I've got four 750GB drives in addition to the installed system drive.
7 >>>>>
8 >>>>> I'd like to aggregate them and split them into a few volumes. My first
9 >>>>> inclination would be to raid them and drop lvm on top. I know lvm well
10 >>>>> enough, but I don't remember md that well.
11 >>>>>
12 >>>>> Since I don't recall md well, and this isn't urgent, I figure I can look
13 >>>>> at the options.
14 >>>>>
15 [...]
16 >>>> What kind of RAID level do you want to use, 10 or 5? You
17 >>>> can also split it: Use a smaller RAID 10 for performance-critical
18 >>>> partitions like /usr and the more space-efficient RAID 5 for bulk like
19 >>>> videos. You can handle this with one LVM volume group consisting of two
20 >>>> physical volumes. Then you can decide on a per-logical-volume basis
21 >>>> where it should allocate space and also migrate LVs between the two PVs.
22 >>>
23 >>> Since I've got four disks for the pool, I was thinking raid10 with lvm
24 >>> on top, and a single lvm pv above that.
25 >>>
26 >>
27 >> Yeah, that would also be my recommendation. But if storage efficiency is
28 >> more relevant, RAID-5 with 4 disks brings you 750GB more usable storage.
29 >>
30 >>
31 >
32 > It looks like I'll want to try two different configurations. RAID5 and
33 > RAID10. Not for different storage requirements, but I want to see
34 > exactly what the performance drop is.
35 >
36 > I wish lvm striping supported data redundancy. But, then, I wish btrfs
37 > was ready...
38 >
39
40 Just out of curiosity: What happens if you do `lvcreate --mirrors 1
41 --stripes 2 ...`? Does it create something similar to a RAID-10 or does
42 it simply fail?
43
44 Regards,
45 Florian Philipp

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Re: [gentoo-user] dmraid, mdraid, lvm, btrfs, what? Michael Mol <mikemol@×××××.com>