new RAID-array: drives from different brands recommended?

[meulie]

Hi all,

I'm about to purchase some drives that will form a RAID-array. Now I have read in various places that it's a bad idea to get all drives from the same brand/model/batch.

Should I really go for something like 1 Seagate, 1 Hitachi, 1 Samsung & 1 Western Digital drive?
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Greetz,
Evert Meulie

[snIP3r]

[overkll]

IIRC, it is recommended to use identical drives for RAID.

[Cyker]

No, the drives have to be THE SAME SIZE, but other than that it doesn't really matter.

They should be of comparable speeds, otherwise all the drives will get bottlenecked by the slowest drive, but apart from that it should be okay.


The reasoning behind the "Use different drives" thing is that multiple-drive failure will "Kill RAID dead!"

So, if you get all the same drives in one go, and it turns out there's a fault with the batch, you might be screwed (Esp. w/RAID0 which is tricky to recover data from, and RAID5, which is near-impossible to recover data from!).

By buying different drives, the chances of a mass-fault are supposedly less, but it's all down to chance really.

My personal take is that RAID stands for Redundant Array of Inexpensive Disks so Ijust buy the cheapest non-crap drives I can lay my hands on (i.e. makes like WD, Seagate, Maxtor, Hitachi, and not makes like Excel and Fujitsu )

[jcat]

I often hear people talk about the possibility of drives from the same batch failing, and I can well believe the theory. But, the chances of more than 1 of a bad batch failing after 1000s of hours run time due to a common fault, and within a windows of say 2 days, are pretty minimal, maybe a couple within a month is possible. And in practice I've never seen this happen (I've sys-admined 100s of different servers).

Therefore, a long as you replace a drive quickly when it fails (within a day or 2), you can't go too far wrong. If you want to be really safe, then keep a redundant spare in the array for quick recovery to full redundancy level, the replace the spare when you can.


I recommend Seagate, as it's the brand I've had least trouble with over the years.



Cheers,
jcat

[eccerr0r]

I'm currently using in my software RAID5:

1 seagate 120G with 8M cache
1 maxtor 120G with 8M cache
1 maxtor 120G with 2M cache
1 post-seagate/maxtor merger maxtor 120G with 8M cache

Performance is not way too bad. The only thing to watch out for is to make sure the geometries match, or don't use the portions of the disk where they don't match. I've found the true maxtor disks are slightly bigger than the seagate-affiliated disks, so I had to use lowest common denominator and use the smallest of the set to make the array.

Personally the disks just need to be close to the same speed as possible, one lagging drive will slow down the array. I've found if I have one disk doing self tests, the whole array's performance tanks.
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What am I supposed watching?

[meulie]

I am considering going for RAID10 (RAID5 would be nicer, but write hole issue has got me spooked a bit, unless a UPS can get me around that?) & using 4x Samsung SpinPoint F RAID drives (HE103UJ).
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Greetz,
Evert Meulie

[drescherjm]

[drescherjm]

[jcat]

Proper RAID controllers have battery backups for their write cache, that prevents any data being lost before it was committed to the drive in the event of a power failure.

However, if there is no battery backup for the write cache you can disable the write cache itself, but I guess that will lead to a slight performance hit. It's the usual balancing act between cost, performance, redundancy etc.. ..the choice is yours



Cheers,
jcat

[drescherjm]

[meulie]

[drescherjm]

[meulie]

Don't you mean 24/7/365.25?
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Greetz,
Evert Meulie

[jcat]

No need for floating point maths here. Lets just say "all year round"



Cheers,
jcat

[drescherjm]

Typing error.
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John

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