Re: Slow queries / commits, mis-configuration or hardware issues?

On 16 Listopad 2011, 2:21, Cody Caughlan wrote:
> How did you build your RAID array? Maybe I have a fundamental flaw /
> misconfiguration. I am doing it via:
>
> $ yes | mdadm --create /dev/md0 --level=10 -c256 --raid-devices=4
> /dev/xvdb /dev/xvdc /dev/xvdd /dev/xvde
> $ pvcreate /dev/md0
> $ vgcreate lvm-raid10 /dev/md0
> $ lvcreate -l 215021 lvm-raid10 -n lvm0
> $ blockdev --setra 65536 /dev/lvm-raid10/lvm0
> $ mkfs.xfs -f /dev/lvm-raid10/lvm0
> $ mkdir -p /data && mount -t xfs -o noatime /dev/lvm-raid10/lvm0 /data

I'm not using EC2 much, and those were my first attempts with ephemeral
storage, so this may be a stupid question, but why are you building a
RAID-10 array on an ephemeral storage, anyway?

You already have a standby, so if the primary instance fails you can
easily failover.

What are you going to do in case of a drive failure? With a server this is
rather easy - just put there a new drive and you're done, but can you do
that on EC2? I guess you can't do that when the instance is running, so
you'll have to switch to the standby anyway, right? Have you ever tried
this (how it affects the performance etc.)?

So what additional protection does that give you? Wouldn't a RAID-0 be a
better utilization of the resources?

Tomas