SSDs, VM SANs & RAID - WAS Re: [gentoo-user] SSD partitioning and migration

[Tanstaafl]

On 2013-07-19 3:02 PM, Paul Hartman <paul.hartman+gentoo@×××××.com> wrote:
> I think you are. Unless you are moving massive terabytes of data
> across your drive on a constant basis I would not worry about regular
> everyday write activity being a problem.

I have a question regarding the use of SSDs in a VM SAN...

We are considering buying a lower-end SAN (two actually, one for each of 
our locations), with lots of 2.5" bays, and using SSDs.

The two questions that come to mind are:

Is this a good use of SSDs? I honestly don't know if the running VMs 
would benefit from the faster IO or not (I *think* the answer is a 
resounding yes)?

Next is RAID...

I've avoided RAID5 (and RAID6) like the plague ever since I almost got 
bit really badly by a multiple drive failure... luckily, the RAID5 had 
just finished rebuilding successfully after the first drive failed, 
before the second drive failed. I can't tell you how many years I aged 
that day while it was rebuilding after replacing the second failed drive.

Ever since, I've always used RAID10.

So... with SSDs, I think another advantage would be much faster rebuilds 
after a failed drive? So I could maybe start using RAID6 (would survive 
two simultaneous disk failures), and not lose so much available storage 
(50% with RAID10)?

Last... while researching this, I ran across a very interesting article 
that I'd appreciate hearing opinions on.

"The Benefits of a Flash Only, SAN-less Virtual Architecture":

http://www.storage-switzerland.com/Articles/Entries/2012/9/20_The_Benefits_of_a_Flash_Only,_SAN-less_Virtual_Architecture.html

or

http://tinyurl.com/khwuspo

Anyway, I look forward to hearing thoughts on this...