----- Original Message -----
| On 09/27/2013 11:25 AM, Kwan Lowe wrote:
| > On Thu, Sep 26, 2013 at 4:28 PM, Antonio da Silva Martins Junior
| > <asmartins@xxxxxx> wrote:
| >> Well, I think this is one of the big examples of what
| >> we can do with LVM: http://www.greyoak.com/lvmdrive.html
| >
| > This is one of the top reasons that I use LVM on my home builds. I
| > generally build with an SSD as the OS disk and a large SATA drive
| > as
| > my /home. When I need a bigger disk, which happens occasionally, I
| > can
| > either add or move up to a larger disk. I tend to just move up to a
| > larger disk as I prefer a single disk to multiple disks for both
| > reliability, reduced noise, and reduced power usage.
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| > http://lists.centos.org/mailman/listinfo/centos
| >
|
| So we can generally say that LVM offers no real drawbacks in terms of
| flexibility, but it seems like we are mostly talking about homebrew
| setups.
|
| What about in a high iops situation? Is there any evidence/testing
| out
| there that might show that there is some overhead of LVM that might
| impact total throughput?
|
We have a cluster that pounds away at the various hardware in our setups and LVM offers a performance statistical difference of about 1-5% for the vast majority of our workloads. Many times it's disk or network that is the limiting bottleneck and for disk it's almost always because of the RAID card. Others have to do with file systems when dealing with hundreds of millions of files in metadata heavy workloads. I have seen these problems with and without LVM for the same workloads.
Since LVM sits on top of the same subsystem that drives your bare metal disks, your MD RAID sets, etc, you would see similar performance there.
Snapshots on the other hand can drastically reduce performance and I would strongly recommend you get rid of them as soon as you can. You don't want to be working in them for long.
A lot of work has gone into LVM and you'll notice when performing a search that most of the performance stuff is a couple years old. Careful what you trust out there.
--
James A. Peltier
Manager, IT Services - Research Computing Group
Simon Fraser University - Burnaby Campus
Phone : 778-782-6573
Fax : 778-782-3045
E-Mail : jpeltier@xxxxxx
Website : http://www.sfu.ca/itservices
“A successful person is one who can lay a solid foundation from the bricks others have thrown at them.” -David Brinkley via Luke Shaw
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