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RDX drives vs. USB HDD Drives for Backup

Posted on 2012-03-21
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Hello,

This is Part 1 of a multi-part question regarding backup technology.   I have an SBS 2003 server that is backed up in the following way:

1) Exchange (roughly 30GB) backed up daily using NTbackup to Dell RD1000 (RDX) drives
2) System and Work Files (roughly 100GB) backed up using Symantec BackupExec to Dell RD1000 drives.  Every Monday run a full backup, then run Incremental backups Tuesday thru Saturday.
3) Work files (roughly 80GB) are also backed up to a USB HDD drive daily using RoboCopy
4) Multimedia Files (roughly 500GB) are backed up to USB HDD drive weekly

I have 4 Dell RD1000 drives (three 160GB and one 320GB) that I rotate on a weekly basis with one drive stored offsite.  

My 160GB RD1000 drives are all being used near capacity.  I also plan to upgrade my server to SBS 2011.  This means I either need to purchase 3 or 4 larger RDX drives at a cost of roughly $250 each, or change technologies.

In terms of archiving, we are a small company and do not pull older data off the server.  Our server has two partitions - one for current projects and one for older.  Both partitions are online and backed up per the above plan.

From what I have read, USB HDD drives have a few advantages over RDX drives.  

1. They are about half the price (a 1 TB USB 3.0 HDD drive sells for $125 or so at Costco while a 1 TB RDX drive from Imation or Quantum is about $250.

2. The USB drives are physically smaller and easier to store - although this is not a big deal.

3. My current RD1000 drive is USB 2.0 while the HDD is 3.0.  Granted, my current server does not have a USB 3.0 port.  The new server will so if I stick with RDX I will need to buy a new external RDX drive that supports 3.0 (another $200 or so).

Here are my questions:

1. Are RDX drives more reliable than USB drives?
2. Are RDX drives faster (do they spin at a faster rate)?
3. Since I re-write the data to the drives once every 4-6 weeks, are the two technologies comparable in terms of data stability?  I have read that disks make poor archiving solutions if the disks are stored for extended periods.  Does this apply to my situation?
4. Does SBS 2011 treat RDX and USB HDD drives the same?  I have read that removable drives do not offer the same backup options as tape drives do.
5. Which technology, if any, can be used with Acronis True Image Echo Server for bare metal restore?

Thanks so much for your help.

Chip

*** Note in my original post I had an error stating that I use REV drives (from Iomega) as opposed to Dell RD1000 drives (RDX technology).  Sorry.
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Question by:MrChip2
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by:dlethe
ID: 37769454
First no such thing as a USB drive.   Look inside the enclosure and you will see a SATA drive with $5 worth of electronics.  No such thing as a USB 2.0 disk or USB 3.0 disk, You have a ATA or SATA disk inside those enclosures (maybe even same make/model of disk)

On any given batch you will find WD disks in seagate enclosures, seagate disks in WD enclosures, hitachi disks in seagate enclosures, ....

There is no standard consistent make/model of disk in any of them, and competitors will change what is inside the enclosures at any time to add a few dollars profit to such a low margin item.

No consistency and lowest possible quality price ... that should tell you about reliability.

None of these technologies are all that reliable.  They are all just the least expensive drive a buyer can get at the time they make new production runs.

I can not comment with firsthand experience on RDX technology, but it is still a mechanical 2.5" SATA drive inside the container, so despite what the marketing literature says, it can't be all that reliable, since 100% of all disk drives eventually die.

If you want reliable backup, then personally, I would get whatever is cheapest and back up more often.  Without RAID1 or some sort of redundant level of RAID then you run a higher probability of getting partial data loss then catastrophic failure anyway, so don't try to address this by throwing more  money at a disk which is only marginally better.

Buy two cheap USB3 enclosures instead of 1 expensive one that is inherently less reliable then a pair of cheaper drives.
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by:MrChip2
ID: 37792264
dlethe,

Thank you for your comments and feedback.  I have a few follow-up questions.  What are you referring to when you say "Without RAID1 or some sort of redundant level of RAID then you run a higher probability of getting partial data loss then catastrophic failure"?  Are you referring to the server or the backup?  The server does have hot swappable mirrored drives.  I thought I read somewhere that it is best not to use RAID for backup as it gives another potential point of failure.

If you are suggesting that I have a backup solution with RAID, I could see having that as an on-site backup.  Can you suggest any specific product that is in the $300-$500 range?

It sounds like you are not in favor of using hard drives.  Do you think I am better off using tape?  If yes, what technology do you recommend if I want to be able to hold 250GB - 500GB on each tape?

Thanks!
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by:dlethe
ID: 37792375
Whomever told you not to use RAID for backup either misinterpreted your question, or is a fool.     Maybe they meant that RAID1 is not a substitute for backing up?  

As for data loss.  It is much more probable to get an ECC error or unreadable block then to have a drive fail.  With disks having hundreds of thousands of spare sectors, it isn't a stretch to consider that maybe sectors still fail but the disk is still usable.  

I am saying that nothing is inherently reliable. That is why you need redundancy.   I remember when I was working for one of the RAID manufacturers when we were learning about this new thing called SATA drives that were going to be marketed for "near line" storage.   None of us imagined that somebody would be foolish enough to put anything important on them unless they were configured for redundancy.  They were just too poorly designed and slow and the ECC logic didn't have enough bits to provide enough data integrity, so we all just laughed about the prospect of using them for anything BUT near line, meaning archiving storage.  They were originally designed for things like virtual tape libraries which would have occasional use.

Doing a backup with RAID1 makes a lot of sense.  Win7 with native software-based RAID1 is just fine, even with consumer drives, as long as you keep backups of backups.  But if you want to protect the data, go with more redundancy, like RAID6 (or Solaris' RAIDZ2).    If you can't do extra redundancy, then at least use enterprise SATA disks.  Those are designed for 24x7x365.  

Remember the desktop SATA disks are designed for 2400 hours annual use, and the level of ECC protection is pretty bad.  That is why you need to go with extra redundancy.
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Author Comment

by:MrChip2
ID: 37793413
dlethe,

What you say makes sense to me.  It does, however, raise some new questions about my overall storage/backup strategy.  Some of these I will ask in a different thread.  For now, I have a few final questions before closing this thread out.

1. Assuming my PE2950's RAID controller will support it (I think the part number is FY387 - Assembly, Card, PERC5I, Serial Attached SCSI, 1950, 2950), in terms of reliability how much better off would I be if I changed the server's internal storage from RAID1 to RAID6 (hot awappable)?

2. Would using an LTO-2 or LTO-3 tape drive for offsite backup be more reliable than the external hard drives?  I know tapes are far superior for shelf life - I just wonder about reliability and ease of data recovery?

3. Is it safe to say that the two 750GB 7200RPM SATA drives that are in my R300 server are enterprise-grade?  The part number for the drives is NW342 - Hard Drive, 750G, Expandable System, S2, 7.2K, 3.5, HITACHI GMN.  If yes, I am thinking I could pull these from the R300 and put them in a NAS box.

Thanks again for your help.
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dlethe earned 500 total points
ID: 37793482
The PE2950 controller is tuned for enterprise SATA disks.   While you *could* put in a desktop drive, when (not if) it goes into a deep recovery that takes more then 7 seconds, the controller will think the drive failed and initiate a failover scenario.   Don't put desktop drives on that controller.  period.  (Google TLER for a full definition).

2. Reliability is a function of many things.   No single all-eggs-in-one-basket is inherently reliable.  Some bozo could spill coffee on it or degauss it because they put a cell phone on top of it.  The tape could get damaged by the loader.  There is no correct answer as a whole because if you just look at ECC and ease-of-recovery, you don't account for the more likely scenario of failed data loss -- human error.  Tapes have longer shelf lives, but what is the likelihood that they stop making a tape drive mechanism to read those old tapes if you don't constantly recycle them every 5 years to a more modern format?

So answer #2 is nothing is reliable. Do as much backup as necessary so that the numbers for risk management work out.  Think of it as buying  health or life insurance.  How big a deductible do you need and how big should the policy be. I can't tell you what the answer is, you have to.

3.  If these came from Dell as part of the factory config, yes they are enterprise class.   Dell won't do a factory config on a server with that controller unless they were enterprise class. They would be just fine in a NAS box.
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Author Closing Comment

by:MrChip2
ID: 37794085
dlethe,

Thank you so much.  All of your responses were helpful!  The drives in the R300 did come from Dell in a server that had the same 24x7x4 hr.  I will assume that they are enterprise class.  If you are willing, keep a look out for some follow-up questions.
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