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Magical Block Store: Why EBS Can't Work

joyeur.com

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Re: Magical Block Store: Why EBS Can't Work

#5

Post by jamie »

jamie wrote: post #3
prodigal_erik wrote: post #2

He didn't touch on Joyent's 2+ day partial outage a couple months ago: http://news.ycombinator.com/item?id=2269329

Don't forget about this: http://www.datacenterknowledge.com/archives/2008/01/15/joyen...

I think both of these links illustrate that errors happen, mistakes happen, software has bugs, and murphy's law always strikes. The question is, when it strikes, do you have enough control to fix the problem? If you've outsourced the solution, does the provider have enough control/knowledge to fix the problem?

These things will get much worse before they get better, and it's best to think of all these abstractions as being a double edge sword.

Re: Magical Block Store: Why EBS Can't Work

#8

Post by blantonl »

I am an active user of EBS on a highly trafficked Web properly, and came from a long and tedious background in enterprise software.

I really think that one paragraph in his blog post summed everything up quite nicely. It could not ring more true:

My opinion is that the only reason the big enterprise storage vendors have gotten away with network block storage for the last decade is that they can afford to over-engineer the hell out of them and have the luxury of running enterprise workloads, which is a code phrase for “consolidated idle workloads.” When the going gets tough in enterprise storage systems, you do capacity planning and make sure your hot apps are on dedicated spindles, controllers, and network ports.

Re: Magical Block Store: Why EBS Can't Work

#9

Post by lindvall »

spullara wrote: post #4

Also worth noting is that Amazon isn't forcing you to use EBS. They also have tons of fast local storage available to RAID as you wish.

I strongly believe one of the most positive aspects of EC2 was that it demonstrated a beautiful philosophy that a node and their disks should not be relied upon to always be around and pushed it into the mainstream.

Even for people who didn't use EC2 the existence of the platform caused more people to rethink their architectures to try to rely less on Important Nodes.

EBS is a step back from that philosophy and it's a point worth noting.

One of the great things this post does is enumerates some of the underlying reasons why relying on EBS will inevitably lead to more failures and in ways that are harder and harder to diagnose.

Re: Magical Block Store: Why EBS Can't Work

#10

Post by blantonl »

smhinsey wrote: post #6
spullara wrote: post #4

Also worth noting is that Amazon isn't forcing you to use EBS. They also have tons of fast local storage available to RAID as you wish.

Do you mean RAIDing local instance storage? I haven't heard of this approach so far, do you have any links?

Depending on the instance that you have provisioned, you have anywhere from 1 to 4 ephemeral (local) disks available to your instance.

They are typically available as /dev/sd[bcde]

In centOS, implementing a RAID-0 block device across 2 ephemeral disks that is present on an m1.large instance can be done via the following:

mdadm --create /dev/md0 --metadata=1.1 --level=0 --quiet --run -c 256 -n 2 /dev/sdb /dev/sdc

You'll then need to format the block device with your fs of choice. Then mount it from there.

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