Questions on RAID10

E

elec999

Limp Gawd
Joined
Feb 11, 2004
Messages
219
I want to build a raid10 with six 1TB hard drive. For raid10 do I need a good controller, or will most onboard sata raid10 do fine. In raid10 can I basically loose upto 3 drives in my six drive configuration. Can I trust Ich9r and windows for array over 2TB.
Thanks
 
Your standard onboard will DO it, but the CPU overhead will be a pain. If you're willing to shell out the money for 6 HDDs, get yourself a good controller while you're at it.

As for trusting it, it should be fine, and Windows has support for a couple TB just fine I believe (don't quote me though).

Just an afterthought as well, but any reason why you're going with RAID 10 over, say RAID 5 or 6? Both of those will give you more space (an extra two or one drives, respectively), are just as safe and perform about the same.
 
In the event of controller failure, raid 10 should still allow him to access the drives.

Anytime you are using more than a couple of drives, you are better off using an external controller. There are few MOBO's that will even support a 6 drive raid of any size.

Don
 
DonDon said:
In the event of controller failure, raid 10 should still allow him to access the drives.
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That's why I was suggesting the separate controller. I've had too many fuckups with motherboard controllers; motherboards can and do fail too often to really make using the onboard controller worth it. 6 disks is the perfect size for a RAID 5 array, and if you get a solid controller (hardware RAID, dedicated buffer, not used; check ebay), it'll run as long as you need it to ;)
 
Umm.. why would you want raid 10 for a setup like that? Any particular reason?


Also, I would recommend a real hardware controller with battery backup.
 
Ockie said:
Umm.. why would you want raid 10 for a setup like that? Any particular reason?


Also, I would recommend a real hardware controller with battery backup.
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I wouldn't mind a RAID 10 myself. The only reason I'm not doing it is I don't have enough room for 4 drives. It a mirrored pair with a stripe of that mirror, What's not to like? ;)

I agree with the battery backup, I wouldn't run without one. I can't say much for how the onboard would perform. It should use about the same CPU as running two RAID 0 arrays, and for me running one RAID 0 array doesn't use much CPU.
 
Well, RAID10 gives you the best of both worlds, speed and reliability. We use RAID10 in all our customers servers but boy, is it expensive. You shell out quite some moolah to setup it up, just to have the storage space split in half. :D

A good controller is really what you should use for RAID10. You don't want to invest this much money and then have the raid hit the shitter because of a mobo problem.
 
ScYcS said:
Well, RAID10 gives you the best of both worlds, speed and reliability. We use RAID10 in all our customers servers but boy, is it expensive. You shell out quite some moolah to setup it up, just to have the storage space split in half. :p
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Yea, but you loose half your disk space. ;) If you get a decent controller, and you're not in an environment where you think either the controller or around half the drives are going to fail, go RAID5 (or perhaps 6) instead; you'll get more bang or your buck.

Speaking of controllers: If you're already getting 6 TB drives, you've probably got another $250; try one of these on for size: You can find them and similar cards on eBay for about $250-300, like here: http://cgi.ebay.com/LSI-MegaRAID-88...ryZ96881QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The LSI 8344ELP is the most common, and can usually be had for about $150, but it's only 4 internal/4 external, though that may work with your setup (route two of the external lines back internally).
 
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I am worried about multiples drives falling that's why I chose raid10, raid5 may take too long to rebuild. And one question what is the purpose of the battery back, if my system will be connected to external battery backup.
Thanks
 
My experience with RAID 5 is that the write speeds suck. I'm sure that is dependent upon many things, but I would go 10, given the choice.
 
The 8888ELP seems to attractive, but the prices for it, not at all. Just curios why no one recommend an Areca card.
Thanks
 
elec999 said:
I am worried about multiples drives falling that's why I chose raid10, raid5 may take too long to rebuild. And one question what is the purpose of the battery back, if my system will be connected to external battery backup.
Thanks
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In this case you are safer with Raid6, really.

With a 6 disk raid 10, you can lose UP TO 3 drives and still be ok, but if one single mirror pair (2 drives) dies, you are screwed.

In Raid6, you can lose any 2 drives and still be ok. Lose 3, and you are screwed. I suppose raid61 would be better....lose any 4 drives and you are ok :)
 
elec999 said:
I am worried about multiples drives falling that's why I chose raid10, raid5 may take too long to rebuild. And one question what is the purpose of the battery back, if my system will be connected to external battery backup.
Thanks
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How many drives do you expect to fail in a matter of a few hours apart? I think you are a little paranoid in the levels of failures.


If you had a 20-100 drive array, I can see your concerns about multiple failures, but you only have 6 drives. If you lost two in such a short period with such a small array, I'd be very concerned.


And since you are worried about failures, you can still lose your entire array with two drive failures with Raid 10
 
xxEIEIOxx said:
I wouldn't mind a RAID 10 myself. The only reason I'm not doing it is I don't have enough room for 4 drives. It a mirrored pair with a stripe of that mirror, What's not to like? ;)
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I am well aware of what Raid10 is, but it has very specific implimentation needs. I just don't see the OP needing such an array compared to say Raid 6 or even Raid 5.
 
djBon2112 said:
Your standard onboard will DO it, but the CPU overhead will be a pain. If you're willing to shell out the money for 6 HDDs, get yourself a good controller while you're at it.

As for trusting it, it should be fine, and Windows has support for a couple TB just fine I believe (don't quote me though).

Just an afterthought as well, but any reason why you're going with RAID 10 over, say RAID 5 or 6? Both of those will give you more space (an extra two or one drives, respectively), are just as safe and perform about the same.
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RAID 10 is so much more faster at writing data and for the most part can read just as fast or faster if the controller supports mirrored reads. You have less overhead with 10 do to the parity drive and it has more tolerance.

The only drawback is the cost of the configuration. However, if you have important data, money, and seem to have crash issues then go with RAID10
 
E7130 said:
RAID 10 is so much more faster at writing data and for the most part can read just as fast or faster if the controller supports mirrored reads. You have less overhead with 10 do to the parity drive and it has more tolerance.

The only drawback is the cost of the configuration. However, if you have important data, money, and seem to have crash issues then go with RAID10
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Alright, makes sense.
 
In raid10 can I basically loose upto 3 drives in my six drive configuration
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Depends on what 2nd drive fails, if its the 1st failing drives mirror, then the whole array is lost. So you can still have 2 disks fail the entire array and lose all your data
 
Ockie said:
I am well aware of what Raid10 is, but it has very specific implimentation needs. I just don't see the OP needing such an array compared to say Raid 6 or even Raid 5.
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And RAID 6 doesn't? I could do RAID 10 with my onboard. A quick search on newegg shows RAID 6 cards starting at about $359.00, with most of them going over $500.00, and into the thousands. I wouldn't go 6 unless is was for a business server needing 24/7 uptime. Not that I wouldn't prefer it. It just isn't practical.
 
xxEIEIOxx said:
And RAID 6 doesn't? I could do RAID 10 with my onboard. A quick search on newegg shows RAID 6 cards starting at about $359.00, with most of them going over $500.00, and into the thousands. I wouldn't go 6 unless is was for a business server needing 24/7 uptime. Not that I wouldn't prefer it. It just isn't practical.
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Yeah, raid10 is common in the intel chipsets and a good alternative to 5. RAID 6 is better than RAID 5 in that it helps the recover time if the disks are large because it doesn't rely on a single parity disk, but is slowwww.
 
xxEIEIOxx said:
And RAID 6 doesn't? I could do RAID 10 with my onboard. A quick search on newegg shows RAID 6 cards starting at about $359.00, with most of them going over $500.00, and into the thousands. I wouldn't go 6 unless is was for a business server needing 24/7 uptime. Not that I wouldn't prefer it. It just isn't practical.
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I agree. RAID 6 isn't needed most of the time, unless you've got a huge array. Most Intel chipsets can do RAID5 pretty well though.

It all comes down to how many drive failures do you need this thing to take vs. the number of drives, and how much space you need. For a 4 disk array,

Maximum safety: RAID 10. Maximum space: RAID 5

If you've got the money to throw it around and that extra drive's space doesn't matter, then yes, RAID 10 is by far your best option. It's fairly safe. If you want that extra space though, RAID 5 is almost as safe for such a small array (small array = less rebuild time, and small array = less chance of more than 1 drive failing).

Also, it can depend on what you're using it for. Backups? Important Data? RAID 10. Fileserving, non-critical data? RAID 5 is more than fine.

Hope that clarifies it a bit ;)
 
I always taught raid6 was just like raid5 except it can add another drive for fault tolerance, and allow more then one drive failure.
Thanks
 
elec999 said:
I always taught raid6 was just like raid5 except it can add another drive for fault tolerance, and allow more then one drive failure.
Thanks
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Yea, that's basically it. It's RAID 5 with another parity drive. The issue is RAID 6 isn't supported on most software controllers (motherboard or otherwise) because of the sheer amount of XOR processing it needs. You'd be looking at $500 for a RAID 6 controller. Which if you're making a large storage server might be worth it.
 
Robstar said:
Raid6 is "Free".

google mdadm.
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Yes, but unless you have a fairly powerful CPU, it'll be slow as hell (at least to write). RAID 6 requires double the number of parity XOR calculations RAID 5 does, and RAID 5 can still strain modern CPUs in larger RAIDs.
 
I did a rebuild yesterday on a be-2350 on my own raid6 and iostat showed my writes at ~ 30MB/second. This is plenty for a low volume fileserver.
 
Controllers I'm currently looking at
areca ARC-1220
3ware 9650SE-8LPML
LSI LSI00138
LSI 8888ELP *favorite so far
Thanks
 
I'd check out the LSI 8308ELP as well; it's the dumbed down cousin of the 8888ELP and does RAID 10 fine.

http://www.lsi.com/storage_home/pro.../megaraid_sas/megaraid_sas_8308elp/index.html

http://www.newegg.com/Product/Product.aspx?Item=N82E16816118091
http://www.newegg.com/Product/Product.aspx?Item=N82E16816118055

Read: Anyone know the differences between those? The more expensive is the LSI00051-F versus the vanilla LSI00051.

EDIT: As far as I can tell the F is ROHS compliant, and that seems like it. I guess perhaps they're just trying to get rid of the vanillas, and hence the low price? It might be worthwhile to snap one up ;) If only I could order form Newegg :(
 
xxEIEIOxx said:
And RAID 6 doesn't? I could do RAID 10 with my onboard. A quick search on newegg shows RAID 6 cards starting at about $359.00, with most of them going over $500.00, and into the thousands. I wouldn't go 6 unless is was for a business server needing 24/7 uptime. Not that I wouldn't prefer it. It just isn't practical.
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I suggested both Raid 5 or Raid 6 but you seem to grab the latter and run with it.


You are arguing over a good controller price, a good controller is REQUIRED regardless of what raid format you are running, it's an assumed expense (especially if you are paranoid enough to feel that you need raid 10). And if you disagree, good for you, but with the space a raid5 solution or a raid 6 solution would save you, would offset the controllers costs... thus you have more space and a better controller.

You say " I wouldn't go 6 unless is was for a business server needing 24/7 uptime", but yet you justify raid 10...

LOL.
 
djBon2112 said:
Yes, but unless you have a fairly powerful CPU, it'll be slow as hell (at least to write). RAID 6 requires double the number of parity XOR calculations RAID 5 does, and RAID 5 can still strain modern CPUs in larger RAIDs.
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Not true. My slow-as-heck laptop does a gigabyte (1034 MB) per second of raid 5 parity calculation. If you've got N disks, you use N-1 times as much parity generation, but that only limits you to (for example) an 8-disk array at 147 MB/s... and my laptop is no speed demon. Raid 6 is slower at only 549 MB/s.
Ockie said:
You say " I wouldn't go 6 unless is was for a business server needing 24/7 uptime", but yet you justify raid 10...
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Since raid 10 is easier to calculate (and this can be a limitation on slow embedded CPUs) it might be better to use raid 10 than raid 6 to get better speeds. Especially if you're using a 4-disk array.
 
Hold on this what is confuse me. For raid10 its easier to calculate, but you still need a good controller to get good throughput and speeds. And raid6 again you need a good controller for calculations. I taught raid10 you could get away with a cheaper controller, but then probably wont get the full speed. Since I am spending good money on the controller. Should I get some 3.5 to 5.25 cages, one that hold holds four 3.5 drives and takes three 5.25 spaces.
Thanks
 
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