Raid From 6 Disks - What Mode Is Best?

Hi,

I have small question - wonder if someone would be able to give me some hint... friend of mine have 6 SATA II Raid-ready drives (longer waranty and hot-plugable)... he cannot have more - all are same vendor, size, and almost serial number as they came in box packed together... just to plug in...

It would be used mainly for securing his programming environment so lot's of small files (also whole system built from source, and general file backups), there would be RaiserFS 4 on disk with 4kb node size so small files would be happy. There wouldn't be too big files, few movies recorded on fly but no file would exceed 1GB... (this makes such big cannon like XFS not best choice and that's why Raiser was choosen - also for it's long known stability)...

now - he decided he want to build Raid matrix... and already have 6 drives but isn't able to plug more on his hardware. It for sure is about data security so it should be mixed method and include Raid 1, but still should be faster than working on one disk.

So... raid 10? Or maybe 0+1 or not with 1 - something like 30, 50?... if there would be 8 disks there could be used raid 100, but there are only 6...

so... anyone have some recommendation?

\G

ps.: first thread after soooo long ... almost forgots how it feels

 

 

 

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You should better tell us the available modes on his device.
I definitively say don't use raid0, because this means "no security, striping only".
Raid1, raid 10, raid1+0 are not the best ones for personal or small buiseness use, because security costs 50% of the total disk space (this means that the 6-disk raid group available capacity will be the capacity of three single disks).
If your disks have RAID5 mode, I suggest it's the best mode. A RAID5 group of 6 disk will will have the capacity of 5 real disks, and it will be reasonably secured because it will survive to the lost of one single disk, and will continue working (without any further security) until the faulty disk is repaired.
So, first of all tell us which RAID types your device can use, mainly tell us if it can use RAID5 or RADI6.
Regards
Yordan

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About 5 then it is supported... about 6 I would have to check to make sure but I don't think so.

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So, I would say that, for your needs, a RAID5 group of 6 disks is the best one. It will provide you with a secured total disk capacity of five time the single disk capacity, and will be able to continue working in case of loss of one of the disks.
In these case, the cost of security is : one disk.
Also, have a look on your RAID specifications, and see if your system can provide a hot-spare.
Then, you can alternatively create a five-disk RAID5 group and a hot-spare.
In this case: the cost of security is : two disk.
The advantage is : if you loose one disk, the missing disk is rebuilt on the hot-spare disk, and you are protected again, you could experience a second crash disk without loosing data.

If you have no hot-spare disk possibility, the system continues working if a disk is missing, but you have no more protection until you repair the faulty disk.

Tell me again if this is not clear enough.

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Sure it's clear, I know the way how raid levels work - just wanted to double check with opinions based rather on experience in that exact case

thanks for your answer Yordan...
\G

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I hope he has a good RAID controller, because generaly, onboard RAID controllers are good for 0,1 and 10, but they are only good at RAID5 when it comes to read speeds. Onboard RAID5 causes a serious write-performance drop (even below the minimum speed of a single hdd) because they lack a good processor.

Ow, and I hope he didn't buy those hdd especialy because they are hot-swapable, because every SATA disk drive can do that .

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Of course, but only disks in a raid group can fail without loss of data. And, of course, the SATA disks you buy have to match the disks matching your raid adapter device.

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You don't need a special set of HDD's in order to get a RAID array. The same brand and size is usualy enough to get a RAID-setup working. You can even combine different brands and size, but then you'll loose space.
The extra warranty is a good thing anyway

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LARGE RAID 6
Raid From 6 Disks - What Mode Is Best?

We have just installed a MD1000 with 15-1TB disks and we need as much space as possible with the best possible protection. I have heard about RAID 6 in some small part, however, I don't know if this is the type of technology that would best suit our needs. I know, from RAID calculators, that instead of using RAID 5 with 4 VD and losing 1 disk per RAID group for parity as best practice, I could create one large RAID 16 with the 15 disks that I have losing, I think, 3 of them for parity and a hot spare. Any suggestions?...

Oh and I have used RAID 10 before and in a high I/O environment we did not seem much of an improvement over RAID5 and our disk space was halved by using RAID10, so my suggestion would be not to go with RAID10.

- Sarge

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