(OT) Questions About SSDs for a Laptop
Michael Butash
michael at butash.net
Fri Sep 5 06:10:36 MST 2014
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 at 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 <michael at butash.net
> <mailto:michael at butash.net>> 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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