Best RAID for 15 x 2TB SAS disks

Lanz

Lanz

Lanz

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This is for a CCTV server, which the data doesn't get backed up on, what what you choose and why? (or is there an Option 6?)
15 Disk Dell MD1000 Enclosure, attached to a Server with a 256MB Perc6E.
2TB 7.2K SAS/SATA = 1862GB
Option 1 (2 x Raid6 Arrays with 2 hot-spares)
Array1: 9310 GB
Array2: 7448 GB
Total: 16758 GB
Option 2 (2 x Raid6 Arrays with 1 global hot-spare)
Array1: 9310 GB
Array2: 9310 GB
Total: 18620 GB
Option 3 (1 x RAID50 Array with 2 hot-spares)
Total: 20482 GB
Option 4 (1 x RAID50 Array with 1 hot-spare)
Total: 22344 GB
Option 5 (1 x RAID6 Array with 1 hot-spare)
Total: 22344 GB
 
mrbell1984 said:
Is this actually been implemented? I would never implement this about of data without some sort of backup.
Click to expand...

Bare in mind it is for CCTV, we also fail to see the need of backups for this particular purpose, RAID redundancy is enough.

If there is an incident the Data would be exported to DVD for viewing anyway.

CCTV in our eyes is really a waste of disk space for most part until something happens.
 
Oh and to answer the question.

Option 1/2: Far too many disks wasted. 2 Arrays of raid 6 = 4 disks unused instantly without hot spares.

Option 3: I fail to see the need of 2 hot spares for this, just and keep it out of the chassis when your spare is used.

Option 4/5 id go for, CCTV all ways will require more and more disk space so depending on how critical the system is to you get the most out of each chassis. Option 4 should be quicker.
 
Your option 3 size is wrong.

If you knock the 2 hot spares off you've got 13 drives left. You obviously can't build a RAID50 with an odd number of drives, so you've got to drop down to 12. I think it should be 18620GB.
 
Laser402 said:
Bare in mind it is for CCTV, we also fail to see the need of backups for this particular purpose, RAID redundancy is enough.

If there is an incident the Data would be exported to DVD for viewing anyway.

CCTV in our eyes is really a waste of disk space for most part until something happens.
Click to expand...

The problem is depends how critical the data is and who is administrating this kind of implementation as cost to fix it will be sky high for a contractor.

I understand about backups possibly not been required but it's playing with a lot of data. Also it would depend on what software is on top of this raid system as well.

It's just a lot of data to be messing about with that is all.
 
Only problem with this is if your building is burnt to the ground you would be able to find out who did it because you have no off site location.

I say location because a backup would be useless..

:P
 
Qu3 said:
Only problem with this is if your building is burnt to the ground you would be able to find out who did it because you have no off site location.

I say location because a backup would be useless..

:P
Click to expand...

Yep, then what happens if the building is burnt in the 'other' location :P It is why I said a backup in the first place unless the backups are been done to tape or something like that, which can get costly.
 
Guys, the vast majority of CCTV systems have no concept of backups or offsite storage of copied media - so this proposal isnt really out of the ordinary.

They either write to VHS or to a hard disk. Then a duplicate is made if the police want to see it. Often the media pool is stored right beside the recorder.

As long as the client or system owner accepts the risks of not having any backup, I'd go with your proposed Option 3. Reasonably safe with a large amount of storage available.

Obviously if backup is an issue you'll need to arrange replication offsite or some kind media based backup for transport offsite. The one instance I've encountered where backup has been an issue for CCTV used replication to central, offsite SAN to work around the issue (but that was an AEGIS system from G4S Secure Solutions at a sensitive site).
 
There is no way to backup the data because of the CCTV software that is used, they design it that way to sell you a extra licenses . If we wanted a backup of the footage, each camera records to two locations - thats your backup.

If we backed up this data, then when you restore it, you just get a meaningless mess of files, you'd have to take a point in time snap of the OS/App and the DATA to get a proper, usable backup.

Your option 3 size is wrong.

If you knock the 2 hot spares off you've got 13 drives left. You obviously can't build a RAID50 with an odd number of drives, so you've got to drop down to 12. I think it should be 18620GB.
Click to expand...

Ah thanks for spotting.

My manager, has opted for RAID6+2SP = 20TB... He said he prefered Raid6 over RAID50...
 
mrbell1984 said:
Yep, then what happens if the building is burnt in the 'other' location :P It is why I said a backup in the first place unless the backups are been done to tape or something like that, which can get costly.
Click to expand...

Depends on the backup and when you are backing it up.. if its once a day the backup is pointless as you've not backed up the footage of the guy burning the place down 5 minutes ago..

Anywho...
 
Qu3 said:
Depends on the backup and when you are backing it up.. if its once a day the backup is pointless as you've not backed up the footage of the guy burning the place down 5 minutes ago..

Anywho...
Click to expand...

Exactly, so if the place gets burnt down all data is gone. Unless the drives are still in tact after the building has burnt down.

It's a waste of money I think but I'm not the one implementing it so. It's the chance you take with CCTV that the data won't be lost any way or another.
 
I say the RAID 5 options. Why?

- You don't care too much about losing the data.
- It places less stress on the system as CCTV is going to be all writes, but sequential. RAID 6 places a lot of stress on disks and systems (1 write = 6 IOPS) while RAID 5 reduces this (1 write = 4 IOPS). Therefore more cameras could be added later o the server used for other things.

RAID 6 evolved to solve the issue with every increasing disk sizes and double drive failures but if you don't care about the data why bother! It just places more stress on the system.
 
Vanilla said:
I say the RAID 5 options. Why?

RAID 6 evolved to solve the issue with every increasing disk sizes and double drive failures but if you don't care about the data why bother! It just places more stress on the system.
Click to expand...

Agreed we use RAID5, 2TB disks and no hot spares. In the event of a disaster where we lost the server. would probably be a natural disaster anyway.
 
Since you're not too fussed about losing the data, option 3 or 4 are fine.

The chances of getting a double disk failure is quite low, although a UBE during rebuild isn't outside the realms of possibility.

RAID6 + 1 GHS is more reliable, but you're dealing with 7.2k disks which (at best) have about 50 IOPs. If most of those are being gobbled up by the constant stream of writes (As Vanilla rightly points out), then performance won't be great. Moreso during a rebuild.
 
Lanz said:
This is for a CCTV server, which the data doesn't get backed up on, what what you choose and why? (or is there an Option 6?)
15 Disk Dell MD1000 Enclosure, attached to a Server with a 256MB Perc6E.
2TB 7.2K SAS/SATA = 1862GB
Option 1 (2 x Raid6 Arrays with 2 hot-spares)
Array1: 9310 GB
Array2: 7448 GB
Total: 16758 GB
Option 2 (2 x Raid6 Arrays with 1 global hot-spare)
Array1: 9310 GB
Array2: 9310 GB
Total: 18620 GB
Option 3 (1 x RAID50 Array with 2 hot-spares)
Total: 20482 GB
Option 4 (1 x RAID50 Array with 1 hot-spare)
Total: 22344 GB
Option 5 (1 x RAID6 Array with 1 hot-spare)
Total: 22344 GB
Click to expand...

Didn't Dell fix the 2TB limit on LUNs like 2 years ago? all of those choices are poor.

It depends what you want? maximum performance? or maximum storage from disks bought - simple.
 
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