Riak on SAN

John E. Vincent lusis.org+riak-users at gmail.com
Wed Oct 2 15:12:14 EDT 2013


I'm going to take a competing view here.

SAN is a bit overloaded of a term at this point. Nothing precludes a SAN
from being performant or having SSDs. Yes the cost is overkill for fiber
but iSCSI is much more realistic. Alternately you can even do ATAoE.

>From a hardware perspective, if I have 5 pizza boxes as riak nodes, I can
only fit so many disks in them. Meanwhile I can add another shelf to my SAN
and expand as needed. Additionally backup of a SAN is MUCH easier than
backup of a riak node itself. It's a snapshot and you're done. Mind you
nothing precludes you from doing LVM snapshots in the OS but you still need
to get the data OFF that system for it to be truly backed up.

I love riak and other distributed stores but backing them up is NOT a
solved problem. Walking all keys, coordinating the take down of all your
nodes in a given order or whatever your strategy is a serious pain point.

Using a SAN or local disk also doesn't excuse you from watching I/O
performance. With a SAN I get multiple redundant paths to a block device
and I don't get that necessarily with local storage.

Just my two bits.



On Wed, Oct 2, 2013 at 2:18 AM, Jeremiah Peschka <jeremiah.peschka at gmail.com
> wrote:

> Could you do it? Sure.
>
> Should you do it? No.
>
> An advantage of Riak is that you can avoid the cost of SAN storage by
> getting duplication at the machine level rather than rely on your storage
> vendor to provide it.
>
> Running Riak on a SAN also exposes you to the SAN becoming your
> bottleneck; you only have so many fiber/iSCSI ports and a fixed number of
> disks. The risk of storage contention is high, too, so you can run into
> latency issues that are difficult to diagnose without looking into both
> Riak as well as the storage system.
>
> Keeping cost in mind, too, SAN storage is about 10x the cost of consumer
> grade SSDs. Not to mention feature licensing and support... The cost
> comparison isn't favorable.
>
> Please note: Even though your vendor calls it a SAN, that doesn't mean
> it's a SAN.
>  On Oct 1, 2013 11:08 PM, "Guy Morton" <Guy.Morton at bksv.com> wrote:
>
>> Does this make sense?
>>
>> --
>> Guy Morton
>> Web Development Manager
>> Brüel & Kjær EMS
>>
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