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Which Controller für a 8x4 TB Raid5 ?

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October 11, 2013 8:39:01 AM

Hey guys,

after reading a lot of stuff i am a bit confused about whats the best solution / hardware for my planned nas-server.

I am planning to build up a backup-server. it mainly only stores backups of other servers and systems and also some files like photos.

My idea was to build it up like this
System: 2x 500GB @ Raid1 connected at the onboard Controller
Data: 5x 4TB @ Raid5 + 1 Hotspare on a extra controller (i want to be able to extend the raid5 later up to 8x 5TB)

It's not needed that the controller is "as fast as possible" and as i said it's "just" a nas-/backupserver so it would be nice, if you also keep in mind that the controller should not be to expensive ;) 

What would you recommend? Or is it in any way a bad idea to set it up like this?


I would be happy to get some ideas and suggestions from your side! Thanks in advance!
- fsmeier
a b G Storage
October 11, 2013 9:41:19 AM

As it will no doubt be idle a lot of the time, I would ...

2x64GB SSDs in raid-1, don't have to be expensive ones, its just for the OS, yes you may lose trim if the SSDs don't support it in raid, but how much a data will you read/write to them ?

Raid controller, don't be a skin flint, if it fails and you can't get a replacement , your screwed.

HighPoint RocketRAID 2720SGL 8-Port PCI-Express 2.0 x8 SAS/SATA 6Gb/s RAID Controller with RAID 6 Support £130

http://www.scan.co.uk/products/highpoint-rocketraid-272...(rr2720)-8-channel-internal-pci-e-20-x8-to-sas-sata-iii-raid-controller-

If data reliability is a must, make suer you get one with battery backup, just in case something screws up.
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a b G Storage
October 11, 2013 10:25:37 AM

For a NAS - Here is what I suggest.

Get a ATOM ITX with Intel NIC - It's 20~30% faster the Realtek NIC
http://www.amazon.com/Intel-D2500HN-Mini-ITX-Motherboar...

HW RAID controller: http://www.amazon.com/Port-Multiplier-SATA-hardware-con...

1x USB pen of 8GB

5x 4TB http://www.amazon.com/Seagate-Desktop-3-5-Inch-Internal...

Install into a mi-tower with 300W PSU

Load OpenFiler into USB pen http://www.openfiler.com/community/download
Create a RAID5 from SPM394+5x 4TB = 16GB usable space or 12TB with Hot Spare.
Connect SPM394 to ITX's SATA port
Power it up
- Make sure the BIOS sets the SATA port as AHCI.
- log in to OpenFiler
Configure the NAS
Turn SMB/NFS/FTP/RSYNC or what ever service that you need

To increase the storage, create another RAID volume.

Although, it's possible to expand the volume, but it take a long time
you have to expand the RAW storage, then expand the partition. lots of thing can go wrong and screw-up the data
Hint: Using RSYNC to automate the backup

It will takes you 30 min to get it up and running
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October 12, 2013 4:48:06 AM

Thank you very much. As i said i have already several components, so your idea (firewire2) is fine but doesn't work for me. Also i want to be aple to expand the volume later.

I think i will switch to a Raid6 Volume and chose the 2720SGL Controller. It also provides really good performance at raid 6 as several tests showed: http://www.tomshardware.de/6gbit-sas-raid,testberichte-...

Is there any difference between 2720, 2720S, 2720SGL ?

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October 14, 2013 10:01:27 AM

With that size array Raid 5 is a no-no. You have a high probability of getting an URE during a rebuild, which will likely lead to you losing your array.

Raid 6 is a better bet, but even at Raid 6 you have a sufficient probability of encountering an error/second drive failure during rebuild (you can do the Markov analysis and tell you the exact theoretical probability based on rebuild times for arrays that size)

Remember, Raid is not a backup solution. Your system will likely get soft errors that will lead to data corruption over time, which is why enterprise-level servers use filesystems such as ZFS with ECC memory to check for errors.

With a raid controller you will need a battery backup to handle the write-back caching they usually do (writes will be buffered until a certain amount of data has been collected before flushing the changes to disk on the controller, if you power goes out you lose those writes)

Honestly if you are trying to build a backup server, I would use ZFS with a mirrored pool and get a motherboard with some ECC memory. This way you have protection against soft errors. You won't get the best value per gigabyte, but your data will be much safer.

For a storage/media server with a SEPERATE backup server, then the RAID6+1 approach would be acceptable...

In response to your previous question "Is there any difference between 2720, 2720S, 2720SGL ?"
After some research it looks like the 2720 standard set comes with cables, the 2720SGL does not, and I can't find much on the 2720S you mentioned.

EDIT: Of course, it really depends on how much you care about that data vs. just wanting it to be available. I handle backups for my research lab, so I am a bit anal when it comes to data integrity.

EDIT2: This will give you an idea of what kind of probabilities you are dealing with, its not a perfect calculator but its good enough: https://www.memset.com/tools/raid-calculator/
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October 14, 2013 12:06:23 PM

Thank you very much for your detailed replay. I think i will try a Raid 6 + Hotspare. I am not so familiar with ZFS and worry a but about dealing with a system i have not worked with yet.
Perhaps i will work with it one time with a test server and change the backupstarage server later.

As is said its "just" a storage server which should store a weekly backup. the newest backups will also stores on a seperate system in addition. So there will be no problem if the system is unavaible or there will be one time (hopefully not but possibly" a data loss.
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