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MichaelP
Jedi Yak
2489 Posts |
 Posted - 2004-12-14 : 09:12:16
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| I've heard some conflicting numbers on the max number of spindles one should have in a RAID array.Does anyone have any real world thoughts / ideas on such?I've been hearing like 5-8 disks in a RAID 5 set, 6-8 disks in a RAID 1/0 set. Does that sound right?How does one get blazing disk performance with SQL server? Several 6-8 disk RAID 1/0 arrays, or one big 14-28 disk RAID 1/0 set?For high performance file serving, has anyone used a RAID 5/0 setup? Does that even make sense to do? That would give you space, speed, and redundancy. Depending on the number of drives in each RAID 5 set, you'd haev to lose quite a few drives to make that setup fail. If you have hot spares, you'd have to have some MAJOR problems before data loss occured.Michael<Yoda>Use the Search page you must. Find the answer you will.</Yoda> |
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derrickleggett
Pointy Haired Yak DBA
4184 Posts |
Posted - 2004-12-14 : 18:55:50
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| I use RAID 5, 10, and 1 only. For RAID 5 I keep it to 6 drives or less. Each enclosure/SAN is different though. On an HP MSA-1000 for example you want to use 5 disks for the optimum performance on RAID 5. On an EMC SAN, you can use 6 with no performance hit. After that, it starts to go down. There doesn't seem to be as much difference on RAID 10, but you pay in cost. Generally speaking, I like RAID 5 for data, RAID 10 for logs, and RAID 1 for the tempdb and OS. I wouldn't ever use a non-standard RAID array. Stick with the basics.Be sure to read the recommendations on each piece of storage hardware. It really does make a difference on the RAID configurations. Sometimes, you want to actually split arrays up so you can take advantage of multiple channels on the device, etc.MeanOldDBAderrickleggett@hotmail.comWhen life gives you a lemon, fire the DBA. |
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keithc
Starting Member
35 Posts |
Posted - 2004-12-15 : 23:33:13
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| This is out of a book I read and unfortunately i have no real world exp but the book reccommend capacity/sizing planning for your disk drives/physical/cpu's and the example was that the OS and SQL Installation files would be fine on Raid 1 then Raid 5 for data files with an online spare then another Raid 1 for log files. This is just a reccomendation out of a book and of course your situation may be different. I don't even know if DBA's out there actually do use capacity/sizing or even establishing a baseline to try and gauge usage to determine what type of hardware they will purchase or Raid solution they will impliment. If they do I'd love to hear on how one does it |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2004-12-16 : 11:39:29
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| Keith, Yeah, that's pretty a standard SQL setup. Unfortunatly, we've grown beyond that and have to get more performance out of SQL server, and a file server. After looking at how some of the really high end benchmarks are conducted, it looks like we'll have to go into what I call "exotic RAID" whih would be things like RAID 50, RAID 100, or even RAID 500 (wow!). Now, to explain that. Lets take RAID 50. You need to setup (2) RAID 5 sets, and then you strip arcoss those two sets. It's great because you get great read performance and better write performance than a single RAID 5 set. I'm still reaseraching these type of setups, so i'll probably report back on how it goes.Michael<Yoda>Use the Search page you must. Find the answer you will.</Yoda> |
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derrickleggett
Pointy Haired Yak DBA
4184 Posts |
Posted - 2004-12-16 : 23:32:21
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| ??? How much IO are you talking about here Mike??MeanOldDBAderrickleggett@hotmail.comWhen life gives you a lemon, fire the DBA. |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2004-12-16 : 23:43:54
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| Much :)Actually, this is really for a High performance file server that needs a sustained throughput of around 1Gbps to start, and then we'll grow to around 2Gbps (thus maxing out the pipe comming out of our SAN).From what I've been told, the average fibre channel drive can sustain around 5MB/sec. This is terrible considering that the drive specs say around 60-200MB/sec depending on what spec you are reading. Anyway, 5MB/sec /drive works out to 25 disks. Pair that with the fact that most RAID 5 sets should be around 5-6 disks or so, I'm looking at (5) RAID 5 sets to make this happen. I think that I'll have a RAID 500 or RAID 5000 to make this a reality. That's four to six 5-disk RAID 5 sets, all striped together. If that doesn't blow up my SAN, it should be pretty fast :) I think that works out to just about 3TB usable space before formatting if using 147GB drives.Way more space than I need, but you can't buy 36GB drives these days.Something tells me that I'm going about this totally the wrong way though. There must be a better way to have really high disk throughput without going to some really exotic RAID setup that noone's ever heard of. I mean, who really needs 1Gbps sustained throughput for hours on end? If anyone has any other ideas about how to do this, let me know!! I'm open to any and all ideas.Michael<Yoda>Use the Search page you must. Find the answer you will.</Yoda> |
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derrickleggett
Pointy Haired Yak DBA
4184 Posts |
Posted - 2004-12-17 : 00:36:00
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| Buy a better SAN. Look at the EMC Symmetrix with a NAS head on it for that type of throughput and file server management. Here's a nice configuration for you I've been thinking about trying for kicks and grins. Take 3 5 disk RAID 5 LUN's. Create three metaLUN's across all three LUN's. Now create multiple backup files and stripe your backups on each of the 3 LUN's you just created. Do the math on that one. :)MeanOldDBAderrickleggett@hotmail.comWhen life gives you a lemon, fire the DBA. |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2004-12-17 : 03:53:46
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| Yeah, that's the sort of stuff I'm talking about!, well if the original RAID sets were RAID 1/0, you'd be taling some serious write performance!Michael<Yoda>Use the Search page you must. Find the answer you will.</Yoda> |
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RAID Array spindles