Re: (OT) Questions About SSDs for a Laptop

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Author: Michael Butash
Date:  
To: Mark Phillips, Main PLUG discussion list
Subject: Re: (OT) Questions About SSDs for a Laptop
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 <
> <mailto:michael@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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