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best reliable raid?

Posted on 2013-02-05
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Last Modified: 2016-12-08
Ive searched the forums but cannot find a definite answer.

I want to co locate a server and backup data to it from remote client sites.

is raid 5 the best ? I want 100% reliable protection so that if a drive fails I can swap it out.

please kindy advise.
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Question by:Ikky786
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Scott C earned 72 total points
ID: 38855203
Read these two articles:

http://www.cyberciti.biz/tips/raid5-vs-raid-10-safety-performance.html

http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/

When asking an opinion question like this you will get many different answers...and from certain points of views they will all be correct.

In the end you will need to make your decision on what you feel is best and what your budget will allow.

In my opinion if you have the money RAID 10 would be best because it provides two layers of protection because you basically have two copies of your data, when you do a tape backup that will be a third.

No solution is going to be 100% safe but you can get pretty close.
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by:dlethe
dlethe earned 214 total points
ID: 38855214
RAID5 can result in data loss by losing even a single drive.  (If you have any unreadable blocks).

For Best reliability - RAID6 AND get enterprise quality disks.  

Remember, 100% of disk drives fail ... eventually.
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by:Kyle Abrahams
Kyle Abrahams earned 72 total points
ID: 38855220
If you go raid 5 it's important to have a few "Hot Standbys" that you can swap in at any time.

A colleague of mine had a drive fail which he RMAd.  While he was waiting for the drive to arrive, a SECOND drive failed, killing the array.

As Scott mentioned, it really depends on your business needs and budget.
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by:sumeshbnr
ID: 38855222
Raid 5 is best .But I haven't heard that someone recovered data from RAID 5 .

Since this is backup server I recommend RAID-1 ,also know as  mirroring, is the technique of writing the same data to more than one disk drive.This is more stable on my experience.See this thread for a clear understanding of    RAID-1 http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/Windows_Server_2008/Q_27907880.html#a38521575
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by:Kyle Abrahams
ID: 38855248
Just to clarify what dlethe was saying:

Raid 5 can recover if one drive fails and the other 2 drives are good.

It CAN fail, however, if one of the sectors that you happen to need on one of the other drives is bad (EG: data got corrupt).
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by:sumeshbnr
ID: 38855305
see this reference also http://babyraj.com/?p=983
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by:dlethe
dlethe earned 214 total points
ID: 38855401
let me clarify what I said.  You have false expectations on the reliability of RAID5.  RAID5 does NOT PROTECT AGAINST DRIVE FAILURES.   It protects against a single read failure on a stripe of data.

If you lose an entire HDD then you will have a single read error on all blocks.  But if you then have an unreadable block on ANY of the other disks then you have data loss if you are degraded.  It is 100X - 1000X more common to have a read error than a drive failure .

That is why you have RAID6, this gives TWO chunks of redundancy for every block of data.  If the data is important, then RAID6.   The risk of RAID5 data loss is profoundly high, especially if you are using a lot of 2TB or higher disks.  Real-world when you rebuild a RAID you put more stress on the surviving disks than they have ever had since the array was created.  There is a much higher probability of losing a drive during a rebuild, or having undetected read errors when degraded.

P.S. I recover data from broken RAID5s all the time in my day job as a RAID architect. It can be done if you are good enough.
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Author Comment

by:Ikky786
ID: 38855501
i see. most great full, I have a HP proliant server with RAID 5. how can I check it for read errors, or better still how can I get it to report to me if a drive fails or if there is a read error.

HP SIM? never set it up but will give it a go.
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by:Scott C
ID: 38855522
You should be able to configure the management software to to notify you of a HD failure and possibly read errors.

It's been a while since I've used their management software so I can't tell you how to exactly.

Also, if your servers are like mine, the lights on a failed drive will show up ORANGE instead of green.
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by:andyalder
ID: 38855736
Your ProLiant can probably do RAID 6 but will require Smart Array Advanced Pack license and cache battery. The ACU will tell tou wnat card you have plus battery status.

I wouldn't bother about HP SIM for one or two servers since the notification drivers plus event notifier can be setup to send you emails without bothering to have a separate monitoring program running somewhere.
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Author Comment

by:Ikky786
ID: 38855766
and just one last question - any links on how to setup the notification on HP servers without HP SIM? many thansk everybody for all your help
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by:andyalder
andyalder earned 142 total points
ID: 38856011
If it's Windows I think the path to configure SMTP is Start/Programs/HP Management Agents/Event Notifier, it does require SNMP to be enabled since it uses it internally to communicate from driver to event notifier.
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by:andyalder
andyalder earned 142 total points
ID: 38857037
Best to mention a RAID level that's even safer than RAID 6, RAID 10 with 3-way mirrors. With that each block of data is stored on 3 disks so you can lose any two plus possibly more. Again HP SAAP is needed and you have to have a huge bucket of cash to pay for all those disks and (as far as ProLiants are concerned) you need the latest generation of controller.
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by:dlethe
dlethe earned 214 total points
ID: 38857097
triple-mirroring is a wonderful RAID layer, and adds benefits of facilitating snapshot backups by breaking a mirror, backing up, then restoring.  

But you can do 3-way mirroring w/o buying SAAP.  Just do RAID1 or 10 with the HP hardware, and use software mirroring on top of hardware mirroring.
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