[lug] LUG Digest, Vol 155, Issue 8

[Andrew Gilmore]

> From: Stephen Kraus <ub3ratl4sf00 at gmail.com>
> To: "Boulder (Colorado) Linux Users Group -- General Mailing List" <
> lug at lug.boulder.co.us>
> Cc:
> Date: Sat, 24 Sep 2016 15:21:25 -0400
> Subject: Re: [lug] RAID1 Versus Mirrored LVM (Fedora 23)
>
> I like RAID, but I also have a ZFS array. ZFS is generally faster, but its
> more dependant on you to ensure the viability of the array info and health.
>
> On Sep 24, 2016 11:09 AM, <stimits at comcast.net> wrote:
>
>> Hi,
>>
>> It's becoming more obvious that I need to dig into details of LVM and
>> RAID. I had originally started out with the intent to produce a mirrored
>> RAID1 on two new disks, and then use that with LVM to divide up the content
>> between "/home" and "/var/www". None of those mount points require booting
>> to them, so this partially simplifies things.
>>
>> Until recently I wasn't even aware that LVM itself can have physical
>> volumes combined into mirrored logical volumes in the same way as RAID1
>> does. So now I'm wondering if it would be wise to remove the RAID1+LVM
>> design and instead just use LVM with mirroring of two ordinary disk drives.
>> Is there anything special about reliability or performance...or anything
>> else...which would influence the choice of RAID1+LVM versus
>> LVM-with-mirroring? Why would I pick one scheme over the other?
>>
>> Thanks!
>>
>

After working through a few of these options, you should know that LVM
mirroring only uses the second mirror for reading if the first fails.
If you want RAID 1 read performance, don't use an LVM mirror.

Andrew
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