Raid 1 is simply giving you redundancy. When, not if, it breaks,
theoretically both shouldn't fail. I have heard of instances where
masses of drives in a dc all purchased the same time began all failing,
taking out clusters as more than 1 disk was dying without any hot
standby, etc.
LVM is giving you flexibility. I don't fully preprovision all the space
on the disk, but I do give it to lvm in the form of a physical volume.
I then create raid, var, var/log, usr, home, whatever at a certain
size. If I outgrow one, I do an lvextend, add data, resize2fs to grow
the ext partition, and done. Usually I end up only growing home, var,
or my ext0 that I use for a dump of vm images and my opt directory
symlinks there.
Shouldn't matter as long as they're comparable, ie. both like samsung 840's.
Here's what my config looks like in use:
mb@hostname ~ $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 477G 0 disk
├─sda1 8:1 0 250M 0 part
│ └─md127 9:127 0 249.8M 0 raid1 /boot
└─sda2 8:2 0 476.7G 0 part
└─md126 9:126 0 476.6G 0 raid1
└─spv0 (dm-0) 252:0 0 476.6G 0 crypt
├─hostname--vg0-root0 (dm-1) 252:1 0 3G 0 lvm /
├─hostname--vg0-swap0 (dm-2) 252:2 0 3G 0 lvm [SWAP]
├─hostname--vg0-usr0 (dm-3) 252:3 0 9G 0 lvm /usr
├─hostname--vg0-var0 (dm-4) 252:4 0 3G 0 lvm /var
├─hostname--vg0-varlog0 (dm-5) 252:5 0 1G 0 lvm /var/log
├─hostname--vg0-home0 (dm-6) 252:6 0 64G 0 lvm /home
└─hostname--vg0-ext0 (dm-7) 252:7 0 128G 0 lvm /mnt/ext0
sdb 8:16 0 477G 0 disk
├─sdb1 8:17 0 250M 0 part
│ └─md127 9:127 0 249.8M 0 raid1 /boot
└─sdb2 8:18 0 476.7G 0 part
└─md126 9:126 0 476.6G 0 raid1
└─spv0 (dm-0) 252:0 0 476.6G 0 crypt
├─hostname--vg0-root0 (dm-1) 252:1 0 3G 0 lvm /
├─hostname--vg0-swap0 (dm-2) 252:2 0 3G 0 lvm [SWAP]
├─hostname--vg0-usr0 (dm-3) 252:3 0 9G 0 lvm /usr
├─hostname--vg0-var0 (dm-4) 252:4 0 3G 0 lvm /var
├─hostname--vg0-varlog0 (dm-5) 252:5 0 1G 0 lvm /var/log
├─hostname--vg0-home0 (dm-6) 252:6 0 64G 0 lvm /home
└─hostname--vg0-ext0 (dm-7) 252:7 0 128G 0 lvm /mnt/ext0
-mb
On 09/04/2014 10:19 AM, Mark Phillips wrote:
Michael,
Thanks again for your comments, they are very helpful. I have been
googling RAID1 and LVM and finding lots of good information.
I really like your idea of a RAID1 for the two SSDs. Does it matter if
one is msata and one is not?
I am trying to decide on the merits of using LVM with the RAID1, since
I only have 1 disk and I normally don't partition it so I don't have
to worry about running our of space until the disk is almost full.
Could you explain to me the benefit of using LVM + RAID1 for these two
drives? How would you partition the drives? My current drive has about
420 GB of data in /home, about 9GB in /opt, and some misc stuff in
/var, all of which I need to transfer that to the new system.
Thanks,
Mark
P.S. One benefit of using both LVM and RAID1 is learning something new! ;)
On Wed, Sep 3, 2014 at 12:33 PM, Michael Butash <[email protected]
<mailto:[email protected]>> wrote:
I really never hit any io constraints on disks honestly since
using ssd's. I watch gkrellm like a hawk and tend to notice if
something is amiss, and disks are never it, unless one dies. I
tend to abuse my system with 32db of ram and chrome and firefox
each have seen using 10gb of ram each, nothing really ever
slamming disks.
Some games/graphics intensive apps that use bitmap caching to /tmp
or somewhere in home I'll give a ramdisk to ease it's pain. This
works well for things like minecraft servers to ease killing my
ssd's prematurely.
I've never honestly benchmarked my disk i/o with raid, crypto,
lvm, and a fs atop them, but honestly until I'm aggravated with a
visible bottleneck, it's doing it's job. I haven't had that in a
desktop setting since going to SSD's, period.
I'm pretty happy with the msata mx100 micron's in my dell laptop
so far. The fact I can have 2x 512gb ssd disks in my 12" laptop
and 16gb of ram is frigging great.
Do yourself a favour, get a usb3 spindle disk for the bulk data
and get a smaller ssd. I used 32, then 64, then 128, then 256,
now up to 512gb disks that I don't feel I'm getting utterly
screwed having to buy 2x for resiliency. Slice your data
partitions adequately and learn to live within your means. You
quickly figure out what data you really need or don't when you
have to add space, but lvm's make that painless. At home I just
do this with a nas direct, but I rsync a lot of stuff against that
for backups and working between laptop/desktop on the road or not.
My worst offenders are email, everyone else's data I carry about
(hoards of data and docs from customers), stupid windoze xp vm as
my visio runtime, and a few games if they go local. I'm fairly
glad being a linux zealot I was weaned off pc games by mid 2000's,
seeing some actually want a few hundred gigs of space these days.
Same reason I don't use win7, they have the audacity to ask for
25gb for a base install, just so I can run visio somewhere. Not
when I have a 64gb drive. and xp is fine as a hypervisor for visio
in seamless vbox mode.
Enter lucidchart, it's actually a decent replacement for visio
now. Then I'm finally free of any real need for windoze at all.
-mb
On 09/03/2014 10:20 AM, Mark Phillips wrote:
Michael,
Great info...Thanks!
Are there any performance (or other issues) between a
raid1with two 1tb msata ssds and rsync between one 1tb msata
ssd and 7200 rpm 1tb hdd? I like the idea of raid1 with two
ssds, but not sure if I am ready to buy 2 1tb ssds. And yes, I
really need a 1 tb drive.....Just consider me a hoarder of
data...;)
Mark
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