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From Edward Capriolo <>
Subject Re: Running multiple instances on a single server --micrandra ??
Date Tue, 14 Dec 2010 17:25:02 GMT
On Tue, Dec 14, 2010 at 8:52 AM, Gary Dusbabek <> wrote:
> On Tue, Dec 7, 2010 at 20:25, Edward Capriolo <> wrote:
>> I am quite ready to be stoned for this thread but I have been thinking
>> about this for a while and I just wanted to bounce these ideas of some
>> guru's.
>> ...
>> The upsides ?
>> 1) Since disk/instance failure only degrades the overall performance
>> 1/6th (RAID0 you lost the entire node) (RAID5 still takes a hit when
>> down a disk)
>> 2) Moves and joins have less work to do
>> 3) Can scale up a single node by adding a single disk to an existing
>> system (assuming the ram and cpu is light)
>> 4) OPP would be "easier" to balance out hot spots (maybe not on this
>> one in not an OPP)
> Sorry for chiming in so late, but another benefit is that it amortizes
> stop-the-world garbage collection across 6 jvms.
>> What does everyone thing? Does it ever make sense to run this way?
> I think it would be a great way of utilizing CPU and memory, assuming
> you can come up with the IO bandwidth.
> Gary.

The biggest deal I see is SSTables, bloom filters, and indexes are
less efficient with 4x 10GB entities verses 1x 40 GB entity . On the
flip side of this, 6x independent disks will be able to seek faster
then a RAID0 disk (because of queuing on the raid0). This might be a
big win since a person with more data then memory is doing much more

Also a cool flip side about a "micrandra" would be taking a hot swap
disk between nodes, this would give you a blade server like effect,
again much more flexibility then a big RAID set. (and of course a
blade server would provide this functionality :)

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