IT question about disc arrays and RAID

[drift_g35]

I am starting to become more of a productive role with my company, working towards being a DB Admin. I asked about a month ago what you suggested the next step be and someone mentions that keeping up to date of arrays was very important. Unaware at how much a whole set up cost I asked my CEO if I could borrow one to play with and learn how they work (I dont know much about them). He laughed and said that our array setup cost about $100,000 with a controller and everything.

So... What I need to know is what less expensive ways can I get some training on this stuff. I was looking online but I dont even know where to start. Does anyone have any suggestions?

Thanks!

[Gman]

You don't need one to learn about them. Most of what you need to know is high-level as to the pro's and con's; how much storage is lost to have redundancy (RAID 1 = 50% vs. RAID5 = 1 disk, etc.), % of reads vs. writes, rebuild times for failed disks, etc.

The management tools for an array will likely change depending on if it's internal storage vs. an external array.

Some basics can be performed with a desktop that has a controller. I have a home server that backs up all of my systems, so I'm not concerned so much about data retention. I used to run HDDs in a RAID 0 configuration for the extra performance, but SSD has made that unnecessary.

[DOC]

3.5" diskettes all the way.

[esaabye]

For DBA's it is all about IOPS which is a function of the disk speed and the number of them in an aggregate. In the old days we would spend lots of time breaking the BD into table groups and speading across different disk types based on performance needs.

Now we buy an san with data progression and let the controllers move blocks around so that the more popular data is on the outside enge of the fastest spindles. Now we are starting to get SSD and large flash arrays with tons of caching at 'reasonable' pricing thus further removing the planning needs.

Take a look at some of the larger san provider sites (EMC, Dell, HP) and some of the niche like Nimble and read the cool-aid. They will all spin it differently but in the end it is a function of speed of disk times number of disk.

[Holger Danske]

Learn the RAID levels and pros/cons. Agree with Essabye it is about IOPs (and latency). You can buy little 4 disk JBOD's with RAID built in for a couple hundred bucks. Also, my buddy was telling me about unraid. They make arrays and offer a free raid sw solution. I have not checked them out, but you may want to look into it if you want a cheap way to learn. If you have any DBA's or Network admins that have been around the block then pick their brains.

[mitch]

One small nit: if you have a raid controller in front of your disks, you can't specify where your data goes at a granularity smaller than the LUN. The old "outside of the spindle" tricks haven't been valid for a number of years. It's still the way to go for making linux raid devices from a bunch of internal disks, though. Google "linux" and "raid" and you should get the software raid how-to. If you have a spare disk you can wipe - there's no reason you can't partition it into 4 or 5 partitions and mirror them to themselves just as a means of learning some of the commands.

Otherwise, this is an exciting time to be in storage. You can now get 100k IOPS on your desktop quite easily with some of the various flash units out there today. I know there are various companies producing well over 1M I/O per second sustained at fiber speed (in this case, newish 8Gb stuff from Qlogic).

If you want something to play around with at home, some of the various projects like OpenFiler and the like are pretty slick. In general it's like horsepower. Sure you can "do raid". How much money do you have?

[ChadAmberg]

If you REALLY want to spend a few bucks and get something to play with, look on Ebay for an older HP or Dell server with a raid controller and at least 4 disks. Probably get it for a couple hundred bucks. With the 4 disk, you can experience RAID 0, 1, and 5 in both 3 and 4 disk configurations.

[drift_g35]

Thanks for all the info. I'm not looking to spend a whole bunch of money. I also have no experience with anything outside of some basic to intermediate IT skills. I'm a software developer currently but the DB side of things are way more interesting to me. I am currently taking a SQL Server class to get the Microsoft certification. I am doing this because its the only way I could get my work to pay for it since we use SQL Server. I am mainly trying to get as much information as I can to do the research. I also want something to play around with that isnt going to cost a fortune and that I can actually take advantage of as a home server or something.

If there are any books that you recommend or really anything you have to offer is greatly appreciated. Thank you!

[Circuits]

The biggest thing with RAID these days is that the capacity is so large, even with hot spares and hotswap, it can take longer to rebuild around a failed disk within a volume than mtbf to the next disk failure. For large arrays you need serious cooling and environment controls to promote the longevity of your unit drives, and a heavy-duty hardware based controller to speed up the writing and rebuilding.

Learning the concepts is relatively easy from whitepapers and wikis available on the web. Specifics of management, performance of hardware and such, will take a lot of familiarization, tinkering and comparison shopping.

[scratchy]

I work for Oracle in storage engineering, I'd be happy to give you a tour and answer questions. Your questions
have complex answers but can be simplified into easy solutions. Shoot me a PM and we can have a tour and QA
session over lunch or beers. Beers preferable