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I'm looking at getting a Synology DS211 for home office use.

After reading about drive compatibility on their website I have several options available with regards to drive.

I'm leaning towards WD drives at the moment. But then I read a comment at the top of the drive compatibility list to always choose the correct drive for your needs with further comments about RAID.

So my question - Is it necessary or recommended to install a RAID spec drive into a synology NAS that I intend to put into RAID 1? What issues could I encounter if I don't, as I think most home market nas' use software RAID I think... does software raid handle things differently?

Differences between raid and desktop drives. http://wdc.custhelp.com/app/answers/detail/a_id/1397

Cheers.

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migrated from serverfault.com Jul 27 '11 at 22:31

This question came from our site for professional system and network administrators.

7 Answers

The key factor to consider is how much time your NAS will spend running, and how much time it will spend powered down. Most consumer grade hard disk drives are designed to spend less than a third of their lifetime spun-up, whereas server / RAID drives are designed to cope with 24x7 run time.

If you intend powering your NAS down when you don't need access to the data, or if the NAS device has very good power saving capabilities which actually spin-down the drives when not in use, you can probably get away with consumer grade disks - but still expect to have to replace them sooner than you would if they were installed in a desktop PC.

If the drives will be constantly spun-up, you would be better spending a little extra and getting server grade drives.

From the drive's perspective, whether the RAID implementation is in Software or Hardware is largely irrelevant - except for that a hardware implementation may complete read / write operations a little faster allowing the drive to spend more time spun-down.

You should also consider a small UPS to protect your NAS, to ensure data write operations can complete in the event of a power failure.

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+1 for recommending a UPS. I'm going to go for that too. –  Matt H Jul 28 '11 at 1:58
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It depends on your needs, and whether or not the NAS is designed for consumer drives as well as raid drives.

I imagine the most common issue you might find is that the drives will not spin up in the amount of time the NAS expects, at which point it will kick the drive out of the array, causing a costly rebuild of the array once you add the drive back into it.

The NAS might also have options that allow you to tune these kinds of timeout values so that this issue doesn't arise.

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Thinking about it, desktop drive class should be ok for RAID 1. since it's a mirror. There is no parity. –  Matt H Jul 27 '11 at 23:44
    
@Matt If it kicks a drive out of the array, it can no longer guarantee that drive is an exact copy of the one still in the array, so it will still have to rebuild. –  Darth Android Jul 28 '11 at 14:03
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What issues could I encounter if I don't

A perfectly functional drive could be seen by the software as having failed.

I think most home market nas' use software RAID I think...

I am not sure about the Synology, but a large number of home NAS devices are just using Linux MDADM underneath. I am not certain, but my Google searches seem to indicate the Synology is just using Linux MDADM and LVM for RAID and partitioning, these are pretty common well know software RAID implementations.

does software raid handle things differently?

MDADM will drop a drives that are responding too slow. Take time to read the review pages for the drives you are looking at. I purchased a set of 5 1.5TB Seagate drives which a very well know firmware problem that made them drop out of a RAID. These days many people use drives in software RAIDs though. If a drive is really bad about dropping out, then you will almost always seem lots of negative reviews on the well know shopping sites.

Should I install RAID spec drives in a home NAS with RAID 1

Just keep in mind what the purpose of RAID is. It is for fault tolerance, and not backup. If you have a system in place to take backups of that NAS (RAID is NOT BACKUP), then using a cheap drives probably isn't a big concern. If you are going to be lazy/cheap and not have backups, then buy a better drive.

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What are 'RAID spec drives'?

If you mean SAS drives, no, you do not have to stump up the cash for them for home single-user use. Normal SATA drives should do, and using RAID will give you some protection against HDD failure.

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paranoid, before answering you might want to have a look here: wdc.custhelp.com/app/answers/detail/a_id/1397 –  Matt H Jul 27 '11 at 22:42
    
@Matt H: I think that information is irrelevant to anybody not using a enterprise-class hardware RAID controller (read more closely), but it would be relevant to companies looking to cutting costs too much. –  paradroid Jul 27 '11 at 22:49
    
The biggest difference is TLER, and that the desktop drives or green drives have been known to be too slow. The software RAID/fakeraid believes this is a drive failure and drops the drive. AFAIK, the biggest difference between the WD RE* seems to be the firmware. –  Zoredache Jul 27 '11 at 23:10
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After reading this, I would buy Hitachi Deskstar 5K3000s.

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interesting link –  Matt H Jul 27 '11 at 23:44
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To answer my own question. I found a really good article here about this subject in detail and relates it specifically to NAS'

Should you use TLER drives in your RAID NAS?

Based on this and the responses this guy received from Synology etc, it would seem that it may not be such an issue at all. It seems that I was correct in assuming that home/small office NAS' use software raid internally and he comments that software raid is more tolerant than hardware raid.

I asked a friend who has a QNAP 4 bay NAS which type of drives he used and he went for standard desktop drives from Seagate.

I have read comments around the web that say that unlike hardware raid, linux software raid (mdadm) will not drop drives that stop responding which would happen if the drive went into error recovery and which TLER is meant to prevent. Therefore a desktop drive will work in a DS211 NAS.

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Drive manufacturers will always, and with some reasoning behind it, recommend higher performance scsi/sas drives over sata i/ii drives. I have four 1TB hitachi drives that were I believe about 100 bucks each in a raid array that I test vm's with esxi off of before putting them in production. The machine has cranked away non-stop for, well, I can check, 202 days, no faults, no errors, great speed. Four 73g 15k/rpm SAS drives are around 190 each. That's 4x73GB (292GB) for ~800 versus 3TB for ~400.

The only thing I recommend is getting matched drives, same speed, size, cache (ect..).

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Many of the WD RAID drives are SATA. Specifically see the RE3 and RE4 line from WD. The connection type ide/sata or scsi/sas isn't really where the difference is anymore. –  Zoredache Jul 27 '11 at 23:13
    
The DS211 NAS doesn't support SAS drives. –  Matt H Jul 27 '11 at 23:24
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