Dell SSDs, RAID 10 and SQL Server

Steviepunk · 26 Jan 2013 at 15:57

I'm looking at server options for a client just now and could use some advise.

This is a replacement for an existing live server that is due for replacement. The server will be running SQL Server, will have approx 6 DBs to run, with the largest being around 50GB in size currently (the others range from 1GB to 20GB at present). The database get's hit heavy during peak time (which ranges from 9am to 8pm).

We are intending of getting 4 x "Dell 200GB SSD SATA Value MLC" in RAID10 configuration (not bothering with the SAS versions of the drives, which come in at almost 3 times the price of those ones!!). This will have the OS and the SQL Databases on it.
Does anyone have any experience with Dells SSD drives? If so, any information on their reliability and performance?

As for the RAID 10 - does anyone know if this operates using TRIM? (will be using Windows Server 2012)
I know I could ask my Dell contact this, but it will take a while to actually get a proper answer (and I'll no doubt have to explain it 6 times as usual!)

We'll also have a couple of 2TB HDDs in to handle backup files and other misc bits and pieces.

Steviepunk · 26 Jan 2013 at 17:03

I don't have IOPS figures, though a check on the SQL stats just now indicates approx 36 reads/writes per second (currently a quiet time) on the main DB. I'll need to tweak my query to seperate out number of Reads and Writes and also get the amount read and written. Not sure how these would translate to actual HDD IOPS.

Will try and get a measure during a busy period as well during the week.

Steviepunk · 27 Jan 2013 at 02:29

iaind said:
What does worry me is that you say this is for a "client" which implies you're selling your "professional" services but don't know all this. With respect, it's maybe best to consider what services you want to be offering people, you don't want to be the one responsible for data loss at someone's business because you didn't do the job properly

We do the software development and we've to put forward what we'd like to see in the new server.
Existing server is 8GB memory and the HDD is under heavy load (as is CPU) - while having vastly increased memory should help SQL keep more of the DB in memory instead of hitting the 'HDD', SSD seemed like a route to look at for improving IO, however I know I don't know a great deal about SSDs for servers hence why I'm asking about it

At £6k for a 4 x 200GB set up with the SSD SAS option, I pretty sure the client will not want to spend quite that much and would probably just go with SAS 15k HDDs instead, however if the 'value' options were going to be up to the job for both performance and reliability then that would be an option we could suggest.

Good point on the end of life in the RAID array, does make the idea of mirroring redundant in that capacity. Will need to consider that if the SSD route proves to be otherwise suitable.

I'll have to have a look at the FusionIO cards as well and see what they offer.

Of course, the client may just want to stick with SAS HDDs anyway since they are a known quantity.

Thanks for the feedback.

Steviepunk · 27 Jan 2013 at 11:45

I don't know the exact spec, but I believe the it currently has a single 4 core Xeon (don't know the model, but probably would have been more or less the top spec 4.5 years ago), 8GB RAM and 4x74GB 15k SAS HDDs in RAID5.

The drive load info it just what I've been told, will be during the week before I can get actual figures on IO performance

Steviepunk · 30 Jan 2013 at 17:40

Still waiting on getting figures through on the IO - hopefully have them tomorrow.

Memory wise, we're going to be recommending going large on that, probabably 128GB should be enough - allows plenty of room for growth over the next few years (and of course can be upgraded later if it becomes necessary) to allow the complete DBs to be held in memory

I light of the feedback provided so far, we'll probably not suggest using the 'value' SSDs anyway, but will need to see the IO data to determine is the SAS SSD would really be necessary or not.

Steviepunk · 31 Jan 2013 at 15:28

Current total sizes Live DB: 75GB
Approx growth over last 4 years: 25GB
Anticipating 50% greater growth over coming 4 years -> additional 37.5GB

Expected DB size in 4 years: 112.5GB

128GB will allow for the live DBs to be held in memory as much as possible for the next 4 years.

If growth is greater than expectations, then more memory can be added as a later stage.

Kelkef - ideally they would upgrade to 2012, however I suspect they'll be sticking with 2008.

Lanz, thanks for that - sounds like a very useful tool.

Steviepunk · 3 Feb 2013 at 23:58

I never claimed to be an expert on the subject, so didn't expect to know the ins and outs of it all, though most places I'd looked suggested that if you can have your DBs run from RAM then it was a good idea to do it. Some interesting information though, I'll be having a further read about some of this though, quite a lot to it all.
As for the server itself, I'm not looking into that now anyway, too much else on my desk at the moment to deal with that.

Steviepunk · 4 Feb 2013 at 17:58

iaind said:
Really, it's overkill 99.9% of the time to have them 100% in memory.

Wasn't saying I didn't believe you, was just saying why I had thought the RAM helped.

anyway, as I said, although I'm not need to spec the server now, I'm still interested SQL Server, so will do some more reading on the best ways to set it up.