SATA SSD vs SAS HDD in 12 node cluster

herbz7 · Feb 9, 2014

Hello,

I am trying to work out whether to purchase SSD's or SAS HDD's to put in a 12 node cluster.

My boss has told me to figure out what's the best sotrage to use. I ruled out SAS SSD's because of the price and I ruled out SATA HDD's becuase I believe SAS HDD's are clearly better and not that much more expensive. (Although I could be wrong about that?)

I was thinking SSD's as I believe they are just as fast as SAS HDD's and use less power and are more reliable and also cost (roughly) the same. (I think?)

If anyone could either confirm or give me additional info to help me make a choice on either SSD's or SAS HDD's that would be greatly appreciated.

Cheers.

HugoStiglitz · Feb 9, 2014

I hope your not comparing a user class SSD (samsung, corsair, crucial & others) to enterprise class SAS drives.

there is so much that is not written on spec pages that comparing them is almost impossible.
whats your turn around in the event of a failure (hours? days? weeks?) whats the estimated lifespan. Remember that user class SSD's have a limited write life. this is not an issue for workstations or home PC's but in a storage cluster it comes up very quickly.

If this is just a beefy home setup then im sure consumer class SSD's will work.
however if its for a business class production enviroment you will want to make sure you are selecting enterprise class SSD's and calculating their limited life into cost of ownership.

herbz7 · Feb 10, 2014

Thanks for the reply, you're right. I didn't take in to account that SSD's have a limited lifespan and them being in a cluster will make that lifespan even shorter. I will compare enterprise class SSD's and SAS HDD's.

Do you think an enterprise SAS HDD would outlast an enterprise SATA SSD (in a cluster)? (As HDD's are susceptible to stop working from vibrations and what not over time however SSD's have a limited write life so I'm not sure.) Also, which do you think would be faster?

HugoStiglitz · Feb 10, 2014

I think the enterprise SSD's will be faster in most circumstances. As far as lifetime you have to consider the warranty period. in a production environment its not advised to have goods in use that are not covered by some type of SLA or warranty. So you have to assume that it will be replaced or moved from production to a development environment(testing) at the end of its warranty period. This is not because it's not going to be fast enough any more but because you cannot ensure the levels of uptime will be met as you have no idea how long or if its even possible to obtain replacement parts.

So as long as it lasts the warranty period without consuming all it's writes your fine. as its use in a development environment will be very minimal.

herbz7 · Feb 11, 2014

Do you (or anyone else) think that the Samsung 840 EVO's (either 500gb, 750gb or 1tb) would be able to take the abuse it would get within a cluster (putting 4 in each of the nodes) or are there better choices of enterprise specific SSD's (that are 500gb-1tb)? Also, if anyone else thinks that SAS HDD's might be a better option than the 840 EVO's feel free to let me know, any help/comments are appreciated.

Happy to provide more information if it's needed.

Oh and if anyone knows, how much difference in speed/performance (or what are the advantages and disadvantages) of just upgrading the server to have SSD's versus upgrading all the nodes to have SSD's. Would it be worth paying 3-4x more to upgrade each node?
What I'm trying to ask is how much better would the performance be as opposed to just upgrading the server?

Thanks.

HugoStiglitz · Feb 11, 2014

No they will not handle it.

Not only that but how long do you have to wait for a replacement? there is not guaranteed replacement time.
Who make the storage cluster? im sure they are able to offer upgraded drives with SLA warranties and turn around times.

In business its equally about speed as it is about replacement turn around.

Think of it this way. If your Evo drives are able to save 1 hour of work a day due to increased speed. but if one dies it takes 2 weeks to be replaced how happy do you think the boss will be having staff sitting around doing nothing?

You don't sacrifice uptime for speed in enterprise environments.

herbz7 · Feb 12, 2014

The wait time isn't that much of an issue here. Who made the cluster is complicated, but we are not associated with them anymore.

I think I've found some decent enterprise SSD's - Intel SSD DC S3500 800gb - 75k/11.5k IOPS even though they are double the price. Do you think it will be worth paying double for these over the EVO's? There's also the Intel S3700 series with 75k/36k IOPS but they're almost double the S3500's again.

I'd love to get some input on how exactly SAS HDD's aren't worth looking in to and shouldn't be used even though they are cheap and there's many that have 1TB storage and apparently they're quite similar in speed however I don't know that for a fact (if you're not sure that's okay).

Thanks for your help so far.

EDIT: They will be RAID 0 in all nodes if that makes a difference.

EDIT2: Oh and most important of all, we want to maximize the performance on 4KB random transfers.

EDIT3: Now I have a better understanding of things I'm going to post a new thread with a more specific question, this one has served it's purpose.

HugoStiglitz · Feb 12, 2014

I really don't think your grasping the idea of uptime.

Raid 0 is a real no no in enterprise. it just takes 1 disk failure or not work correctly to corrupt or lose the entire array.
yes you could have backups but its still going to take you hours / days to rebuild the array and restore the data.

Look into RAID 5, 6 or 0+1

being you are not associated with the vender any longer does the rest of the cluster have any warranty or guaranteed response time?

At the end of the day the choice is up to the owners. I just know I would not want to have anything to do with an infrastructure using home user class equipment with warranty wait times of a week or longer.

There is a reason the enterprise class gear costs more, it has better warranty support. it has better life time expectancy.

User class equipment is designed for occasional use few hours a day or so. enterprise class equiptment is designed to be on and in use it's entire working life.

this is why servers have dual power supplies, ECC ram
why SAN's have redundant raid controllers
and why virtual environments have failover servers in a cluster.

BECAUSE UPTIME IS KEY

herbz7 · Feb 12, 2014

We were using the RAID10 but the boss decided to change to RAID0 because WE DO NOT CARE ABOUT THE DATA (that much). We do not use the cluster every day. We do not hammer it 24/7. I have said several times I will be picking enterprise class stuff. Those Intel S3500's are enterprise class, as well as the S3700's. I've been trying to explain we are barely an enterprise, we just want semi-reliable drives. I already told you it doesn't matter if the cluster goes down for several weeks. We would just like to get a few years use out of them.

All I wanted to know is that are the S3500's are reliable compared to most other SSD's on the market, or is there something else out there. Please stop telling me uptime is key, it is not where I am working. We use the cluster occasionally, speed is key, large storage is close after that and them also being reliable comes after that. Are you telling me the Intel's are rubbish too? If you know of something better please suggest it. If you don't know the answer that's okay but I really don't need another post rambling on about uptime and not answering my questions though, thank you.

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