Raid in Dell Precision M4800 Mobile Workstation

rycliff

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May 21, 2015
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Greetings,

The Dell Precision M4800 Mobile Workstation supports up to two 2.5" SSD drives and one mSata.

I'd like to setup a RAID-0 SSD at 512 gb each on the two 2.5" drives with the mini sata at 1 terrabtye mirroring the entire 1-terrabyte array for data redundancy.

Questions:

1. Is this possible?
2. Will I lose performance because a single drive (the mini sata) will be attempting to mirror in real-time the data of two separate drives?
3. Does this raid scheme have a name?

Thanks
 
This sounds like a RAID 0+1 (a RAID 1 of two RAID 0's) but since it isn't two RAID 0's not isn't really a RAID 0+1 which it doesn't offer. Just RAID 0 1 and 5. You could do a hardware RAID 0 of the two 512's and then do a software RAID 1 of the 1TB and the RAID 0 (only works with Pro version of windows or higher which I'm sure you have since you can't get them with home editions anyways.

That is really your only option.
 

rycliff

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Thank you for your response.

I see RAID-5 is an option. Maybe I'll go that direction. Never done that before--only RAID-0 which is the performance I'm accustomed to. I'm looking for something faster than a single SSD, but with rock solid data reliability.
 
If you get a RAID 5 don't get a 1TB mSATA unless you get 1TB SSD"s as well. All drives MUST be the same size OR it will use what ever the smallest size is.

If you have 2 512's and a 1 TB the 1TB will only be able to use 512 to match the other two. Also in a RAID 5 you have the Sum of all the drives - 1 of space. So if you ahve 3 1Tb's it is 3TB - 1TB so 2TB of usable space so you are pretty much trowing out a full TB that way.

So I would either get them all 512's or all 1Tb's depending if you need the space or the redundancy. If you do all 512's you will still have the same amount of space you would of had in your RAID 0+1 which is 1TB. If you do all 1TB's you will have 2Tb's total.

Just trying to save ya some money if 1Tb is all ya need
 

tedoshea

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In a RAID 0 or 5 configuration on Dell M6800, does it mater if mixing a 1Tb Samsung 850 EVO mSAta with two 1Tb Samsung 850 EVO sata 2.5" drives, or do the second and third drive need to be 1Tb Samsung 850 EVO mSata drives in a 2.5" caddy for mSata?
 

N0BOX

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I doubt the "hardware" would allow you to create a RAID 0+1 out of two 512GB drives and a 1TB drive. As was mentioned, you could use the Intel RAID to set up a RAID 0 array between the two 512GB SSDs then you could set up a Windows "dynamic disk" as a mirror between the RAID 0 array and the 1TB SSD. Unfortunately, you would then lose the speed benefit that you would have gotten from the RAID 0 array, since you would have to wait for mirroring to the single 1TB SSD. You would also lose some of the read performance that an intelligent RAID system would get from treating a RAID 0+1 as a 4-disk RAID 0 for the purpose of reads.

You could set up a 3 SSD RAID 5 array, but in my experience these motherboard RAID arrays just don't give you very good performance, since all the parity calculations come from the CPU. I have used RAID 5 arrays on the Intel RSTe system, and I can't say I noticed any more performance than a single drive (though I was using 7200rpm hard drives). It did save me from a rash of dying drives, though, so it does provide good protection from data loss, while keeping you running while you are replacing the drives (and saves you the time of a backup restore, which you obviously have, also).

You can treat an mSATA SSD exactly the same as a 2.5" SSD when it comes to a RAID array. All you really need is for all the drives to be the same size (after the manufacturer has set aside some of the advertised space for wear leveling). So, if you have three Samsung 850 EVO SSDs, and one of them is an mSATA version, the RAID system won't know the difference. Since they were all created by the same company and they are all the same model, they will all have the same usable size for data. It is advantageous to use drives that have the same read/write performance as each other, since that will make sure one drive's lower performance isn't pulling the other drives down. No point in buying one good drive if the others are just going to bottleneck it.

You might consider putting two 512GB drives in a RAID 0, then using a 1TB drive as a simple backup location. This would allow you to take advantage of the excellent performance of the SSDs in RAID 0, while keeping your data safe. You could use a cheap hard drive, and you could just have your drives run an incremental backup overnight. That would not only protect you from a drive failure, but also from an accidental deletion. The only disadvantage would be that if a drive does fail, you would have to wait until it was replaced before you could continue working. If you aren't dependent on the laptop for work, or if you can go a day without your data, then you aren't really being served well by the redundancy of a RAID array. You are then just using it for backup purposes, which isn't what RAID is for.

I hope this helps! :)
-- Matt