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RAID failure question

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February 28, 2013 1:28:06 PM

I'm looking into getting a Dell Poweredge 2950 rack server with a PERC 5i RAID controller, because i was told that the PE has a maximum of 6TBs for installed drives, and i was planning on going higher than that down the road. I want to eventually setup a RAID 1 to mirror the content i have an my storage drives in the server, but it won't happen immediately. So i was told to setup each drive as RAID 0 temporarily then switch over the RAID 1 when i'm ready. I'm planning on having 2x 2TB drives set as this RAID 0, and down the line, i'll get 2 more for mirroring to RAID 1. First off, can i switch from RAID 0 to RAID 2 without data loss? Is there a danger with setting each single drive as a RAID 0 for the time being?

On a side note, if i have this controller installed, could i just leave it unconfigured but install more than 6TB total in the server?

Thanks

More about : raid failure question

a b G Storage
February 28, 2013 1:41:42 PM

When you reconfigure a RAID array - you will lose the data stored on the drives, so you will need to plan for that. The RAID controller selected optimized for SAS drives, 8 drives total.

Raid 1 will mirror drives, so if 1 drive fails, you can swap the drive and rebuild the array quickly. If 2 drives fail, you can lose the array. Backups are still needed.

Make sure you have enough backup space allocated for rebuilding the array if you go from RAID 0 to RAID 1.
February 28, 2013 1:49:33 PM

Ok so going from RAID 0 to RAID 1 will lose all my data, could i configure RAID 1 without having a 2nd drive for the backup immediately available?
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a b G Storage
February 28, 2013 2:24:09 PM

You will lose data reinitializing arrays. I use three types of RAID in the systems I manage:

RAID 10 (striping/mirrored) - used for mission critical data where the largest volumes are needed, almost zero downtime, and high visibility. If a drive crashes, you replace and rebuild the array - quick recovery time.

RAID 1 (mirrored) - used for data integrity, large volumes aren't as important (you can't stripe the drives), and high visibility. If a drive crashes, you replace and rebuild the array - quick recovery time.

RAID 0 (striped) - used for large volumes, where if a drive crashes, you create a new array, and restore from a backup.
a b G Storage
February 28, 2013 2:25:52 PM

Even with RAID 10, backup the data. It is possible to lose 2 drives at once, and the entire array crashes. It is unlikely, but it can happen.
February 28, 2013 2:41:21 PM

Ok, would i be able to assign RAID 1 to a drive, without having the backup drive installed yet? I won't be able to purchase them immediately
a b G Storage
February 28, 2013 2:44:47 PM

You must have 2 drives for RAID 1 to set it up.
a b G Storage
February 28, 2013 2:46:20 PM

A RAID 1 array is defined as two drives, mirrored. You can't add more than two drives to a single array - if you had 8 drives, you would have 4 arrays.

RAID 10 would allow for all 8 drives to be configured as striped/mirrored in one array.
February 28, 2013 3:06:59 PM

Ok, so this being the case, what do you recommend i do? I don't have the funds to purchase all the drives at once for the backups, only enough for the drives i need for my data expansion. Maybe if i explain my situation a little further, it might be easier to understand my predicament:


I currently have a PowerMac G5 running OSX 10.5 Leopard with a 3TB drive housing all of my media. I also have a Dell Precision T3400 in which i have a mirror of the PowerMac, but i do the backups manually. It's a media center in which i share Movies and TV Shows over our HAN to wireless deivces and wired as well via XBMC.

So I'll be graduating from college in May in the IT field, so i'm looking to purchase a rack server so i have something i can easily add more storage to, and learn Windows Sever 2012 as well. So i was looking at the Dell Poweredge 2950iii because it fits my budget and i found a good customizable deal on Servermonkey.

As far as populating the drives in the Powerdge, I'm planning on taking 2 drives out of my Precision, one a 300GB SAS 15K which i'll use for the OS, and the second a 2TB SATA which holds a ton of data to be used as the first data drive.

Now i read that the 2950 has a max internal storage of 6TB, unless i had a PERC controller installed. I'm trying to figure out whether or not i should fill it to the brim with drives then get a Powervault for RAID 1 and use the 2950 as a Non-RAID, or do a RAID 1 with the data drives.

Initially, i'll be installing the 2 drives i spoke about, and then purchasing another 2TB for the overflow of data that the first is running out of. So that'll be 3 slots take up in the server, 1x 300GB SAS for OS, and 2x 2TB SATA for data serving. So what i'm wondering about is if i put more drives in, would it truly only see up to 6TB, or can i unofficially put more in? Upon talking with someone on the Dell forums, i was told that i would need to assign a RAID type to each drive if i wanted to go higher than 6TB. So if i assign RAID 0 individually, he said i could easily switch to to RAID 1 later without losing data if i choose to mirror the drives. Is there any dangers to assigning RAID 0 to each individual drive?

Given my circumstances and what i'm looking for, how should i go about building the server, do a RAID 0 on each drive to go above the 6TB total, do a non-RAID and just use the 6TB, do a RAID 1 even though i don't have 2 more 2TB at the moment, that would come later.

IF this is all over the place, do ask questions, thank you
a b G Storage
February 28, 2013 3:28:19 PM

Reading through your post, this appears to be a home project - correct? Going under that assumption, if this isn't going to be a production level server (i.e. serving files to clients - just your personal use), my suggestion would be to skip purchasing a server, and build a regular PC - you can load Windows Server 2012 on the PC. Server class machines are built more for 100% reliability in business situations, and for a home use machine, other than touching the hardware with your hands, you probably won't notice a difference between hardware.

For creating the volumes - it would also be less expensive to use standard SATA drives in a software RAID 0 (if you need a single volume assigned to multiple drives) - this allows for less expensive drives, and more storage.

Use a product like SyncBackPro (required for servers) to backup your data.

http://www.2brightsparks.com/syncback/sbpro-features.ht...

It is $54.95 for the license - and you can backup daily (both incremental and full) or synch the data between drives.

By building this all in a PC chassis, you are almost unlimited to the amount of storage you can add to the system - and probably build it for less than 50% of the cost of the server class machine.

Another note - Windows Server 2012 has a 6-month trial period, this would give you enough time to test the server configuration, and learn the software.

The PC route would keep your budget in check, give you more hard drives for the server, and you would still have a good experience learning the server software.
February 28, 2013 4:53:41 PM

I honestly still would rather have the server environment at my fingertips, because i'm looking to do virtualization and DHCP as well. But yea, it will be a home project. My budge is about $400 for now, so 865 is pretty high. I actually already have a license for Windows 2012 because my school gives us access to MSDN, so that's taken care of. Like i can get this server for $400 shipped without the drives.
a b G Storage
February 28, 2013 5:09:13 PM

The Poweredge 2950 is a discontinued model, most of what you may find out there are refurbished units. Typically they were configured with dual Xeon processors around 2Ghz. You find quite a few refurbished units out there. They are also designed to be rack mounted, so if you don't have a rack for them, make sure they are mounted with proper ventilation.

Windows Server 2012 will run on almost any computer built in the last 4-5 years, suggested you have at least 8GB RAM with it. I work with quite a few servers, all of them are in the cloud now - I never touch the hardware.
February 28, 2013 6:32:47 PM

I personally don't like the idea of cloud computing yet, but i think i'll mess around with that functionality in 2012 and see if i can warm up to it. These are actually the specs i'm looking at for the machine:

2x 2.33Ghz Quad Xeon E5410 CPUs
8GB RAM
6x blank drive caddies
PERC 5i RAID card
DRAC 5

All for $400 which includes shipping. That's fine for me with it being refurbished, especially considering my Precision was refurbed and it has been great. I was actually planning on hanging this thing on the wall with these special brackets, we actually have them in our new media room at work, it's pretty cool.

Now i think i figured out a minimized version of what i wanted to ask:
Can I set each drive as raid 0 to trick bios and go past max internal storage? And here's another idea too, i keep most drives in Non-Raid, and when i'm at the point to go past the 6TBs, then i'll do the RAId 0 stuff and perhaps use symantec ghost to clone the drive without using RAID at all? Don't really know if i would need the PERC card in this case though, i might go with the Dell 6ir card instead.
a b G Storage
February 28, 2013 7:40:33 PM

Not a bad price. My experience with RAID and hard drives is this - they don't like being reconfigured to different RAID settings.

You will probably need to invest in a SAS SFF-8484 to 4xSATA cable (they are around $10), and you should be able to add drives of 2TB to the card (standard SATA II drives). Otherwise, you must buy SAS drives which are a bit more expensive. With that cable, you should be able to add a total of 8 drives to the array, in RAID 0, that would be 16TB.

Since not many people use this hardware in non-production server scenarios - it is difficult to find information on the card/system. You can always give it a try and see what happens.

I have always either purchased a configured server by DELL, or used cloud servers (this is a more expensive route - but I don't have to have an IT team or worry about hardware failures). From my experience it is fully secure as having it in a rack next door.

If you reconfigure the RAID system - my suggestion would be to backup the data. I haven't used Norton Ghost in a while - typically I setup a temporary storage, back up the data, then try to configure the RAID. If everything is still there - GREAT! If not, I simply restore the data. One great thing about the cloud - I click a button for image - it creates a full image of the drives, then I can reconfigure and restore if needed. It is about a 50-50 shot...
March 1, 2013 4:07:11 PM

I think i'm going to buy it and see what happens. I did speak with someone at the company, and they said that the stock controller, which is the Dell SAS 5/i non-RAID controller, will accept SAS and SATA drives, and will be able to house my 2TB drive, so that's good.

In your opinion, which HDD controller should i get:
stock as mentioned above
Dell SAS 6/ir SAS/SATA RAID 0,1 for $15
PERC 5i 256MB RAID 0, 1, 5, 10, 50 for $40
PERC 6i RAID 0-60 256MB BBWC Cache got $60
a b G Storage
March 1, 2013 5:28:25 PM

For learning experience purposes, and serving up files for home use, I would suggest the Dell SAS 6/ir SAS/SATA RAID 0,1 for $15. You will be able to utilize RAID 0,1.

Production environments where more than 10 or 20 people are accessing the server - it would be a good spend to get the PERC 6i.
a b G Storage
March 1, 2013 6:31:03 PM

mknabster said:
I'm looking into getting a Dell Poweredge 2950 rack server with a PERC 5i RAID controller, because i was told that the PE has a maximum of 6TBs for installed drives, and i was planning on going higher than that down the road. I want to eventually setup a RAID 1 to mirror the content i have an my storage drives in the server, but it won't happen immediately. So i was told to setup each drive as RAID 0 temporarily then switch over the RAID 1 when i'm ready. I'm planning on having 2x 2TB drives set as this RAID 0, and down the line, i'll get 2 more for mirroring to RAID 1. First off, can i switch from RAID 0 to RAID 2 without data loss? Is there a danger with setting each single drive as a RAID 0 for the time being?

On a side note, if i have this controller installed, could i just leave it unconfigured but install more than 6TB total in the server?

Thanks


I suggest a different approach...

Get 3x 2TB create a RAID5 then expand when you need more space
Pretty straight forward add a drives and expand

March 4, 2013 12:57:10 PM

ronintexas said:
For learning experience purposes, and serving up files for home use, I would suggest the Dell SAS 6/ir SAS/SATA RAID 0,1 for $15. You will be able to utilize RAID 0,1.

Production environments where more than 10 or 20 people are accessing the server - it would be a good spend to get the PERC 6i.


All right cool, i'll do that then. Do you know what the 256MB cache option does on the PERCs? Dell said that they help with moving large files when in RAID, is that true? Some of the files i have are multiple gigabytes in size.

Best solution

a b G Storage
March 4, 2013 3:42:25 PM
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Usually "large files" are 20GB+ in size, and if you were moving files all the time, it might be a good idea. An example would be text files that are being processed into a database, where they must be unzipped, imported into the database, moved to a processed folder, zipped and the text deleted. Running in a 24/7 environment, with file sizes that are large - you would get a noticeable difference.

If you are like me, who has about 500GB of data split among 3 computers, some files being larger than 10GB (DVD, BluRay, TV shows etc), they are moved once in a while, and waiting 2-3 minutes for a transfer (you might save 30 seconds with the controller), in my opinion, it wouldn't justify the costs.
March 5, 2013 1:13:36 PM

Best answer selected by mknabster.
March 5, 2013 1:13:41 PM

I see your point, sounds like a plan then. Thanks so much for your time in answering all of my questions Ron, i appreciate it!
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