Fun with RAID

  • grinch2171
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Post 3+ Months Ago

When you have over 2 PB of storage, it is inevitable that you will have some of it not being used. Being the nerd that I am and bored as hell at work this week, I decided to play around with storage and various RAID levels to see what I can do. I found that I had two 16TB iSCSI SANs sitting around not doing anything so I chose those to experiment on. A lot of talk has been going on in the office about drive performance and whatnot and someone suggested we use RAID-10 for our SQL servers. I have never built a RAID-10 so gave it a shot. Here is what went down and the madness I have created.

The 16TB SAN has 16x 1TB Western Digital SATA drives in it. So what I did is created 8 Logical Drives (LDs) consisting of two 1TB drives in a RAID-1 configuration. I now have LD1-8. Next I created 4 Logical Volumes (LVs) consisting of two of the LDs in a RAID-0 config. This gave me 4 RAID-10's on each SAN for a total of 8 RAID-10 volumes.

On my Windows 7 Enterprise desktop I connected to the LVs and sure enough I get 8 RAID-10 drives. Being the nut I am and knowing that you can also create RAID configs within Windows, I then created a Striped array consisting of the 8 RAID-10's which gave me one big RAID-100. Total drive space ended up being about 7.5TB.

Not being done with what I created, I destroyed the software based striped array and created a mirrored array which gave me a RAID-101 which at the moment I can't find any data on.

Once again I was not done. I destroyed the whole operation and then created 4 RAID-6 LDs consisting of 4x 1TB drives on the SAN. Then created two LVs consisting of two RAID-6 LDs which gave me two RAID-60 LVs. I am now in the process of striping them together to create a RAID-600 which there is no data on the interwebs talking about it. I am not sure if I will try creating a RAID-601 yet. Total usable drive space for the RAID-600 is almost 15TB.

This is what happens when a Systems Engineer gets bored at work and has too much equipment lying around. There is some practical application to this though so it was worth playing around with. The SANs themselves are not the best on the market, they are cheap with a lot of raw storage. They are lacking key feature sets like replication, deduplication, snapshots, and other cool things the big boys like EMC and NetApp can do but they do serve their purpose. I'd much rather do this in Fiber Channel than iSCSI but I work with what I have. I'd also rather have either 15k RPM SAS drives or solid states but SATA is way cheaper.

Oh well, thought I would share some of my madness with everyone before the New Year.
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Post 3+ Months Ago

  • Bigwebmaster
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Post 3+ Months Ago

Sounds like an interesting experiment. So what did you learn in the end from doing all this?

I read a bit on this, and it sound like RAID 100 is a popular choice when it comes to having a very large database.
  • grinch2171
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Post 3+ Months Ago

So far I haven't learned anything except that I can do this. We do have some SQL databases that are pretty big and the main reason for this experiment was to see if I could create a RAID-10 array. The problem with RAID-10 is size. You need a minimum of 4 disks to do this and the biggest enterprise drive you can get is a 3TB SATA drive. But for SQL performance you don't want to go that way. SAS and solid state capacity is well below 3TB so a high performance RAID-10 isn't going to be very big and it will be expensive. This is where the RAID-100 comes in.

To really test this I would need to set this up on a server, enable multi-path, segregate the iSCSI traffic from the LAN traffic, and see what kind of I/O I get from the various RAID configs.

The RAID-600 was more or less to see if I could do it. I don't think it is practical but it would require testing I/O.

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