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From Jonathan Shook <jsh...@gmail.com>
Subject Re: SSD vs. HDD
Date Wed, 03 Nov 2010 20:44:55 GMT
SSDs are not reliable after a (relatively-low compared to spinning
disk) number of writes.
They may significantly boost performance if used on the "journal"
storage, but will suffer short lifetimes for highly-random write
patterns.

In general, plan to replace them frequently. Whether they are worth
it, given the performance improvement over the cost of replacement x
hardware x logistics is generally a calculus problem. It's difficult
to make a generic rationale for or against them.

You might be better off in general by throwing more memory at your
servers, and isolating your random access from your journaled data.
Is there any pattern to your reads and writes/deletes? If it is fully
random across your keys, then you have the worst-case scenario.
Sometimes you can impose access patterns or structural patterns in
your app which make caching more effective.

Good questions to ask about your data access:
Is there a "user session" which shows an access pattern to proximal data?
Are there sets of access which always happen close together?
Are there keys or maps which add extra indirection?

I'm not familiar with your situation. I was just providing some general ideas..

Jonathan Shook

On Wed, Nov 3, 2010 at 2:32 PM, Alaa Zubaidi <alaa.zubaidi@pdf.com> wrote:
> Hi,
> we have a continuous high throughput writes, read and delete, and we are
> trying to find the best hardware.
> Is using SSD for Cassandra improves performance? Did any one compare SSD vs.
> HDD? and any recommendations on SSDs?
>
> Thanks,
> Alaa
>
>

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