Choosing which type of drives to use for what

[HDRW]

I've had a look at all the FAQs and searched the forum, but haven't seen my query addressed, so here goes...

 

I'm building my first unRAID (using a 4-bay HP microserver) and I have a number of different types of drive available, but don't know which to use for what.  I have:

 

WD "Network" (Red) drive - doesn't specify a spin speed but says it's designed for RAIDs of up to 5 drives (how would it know?).

WD "Performance" (Black) drive - reckons it's the Bees Knees for performance (7200RPM etc) , but presumably power hungry too.

WD "Mainstream" (Blue), a sort-of everyday disk for desktops, I think.

Various 7200RPM drives such as Seagate 7200.12

 

There's also a 2.5" WD Blue drive installed under the CD drive, but I assume that's not much use with unRAID (wouldn't be much good for Cache, I believe).

 

Reading how unRAID works, it looks like the Parity disk is worked the hardest, especially when writing, but does that mean the "Black" would be the best choice for its performance, or the "Red" because it's designed for the job?

 

So for the gurus:  If you had one WD Red, one WD Black, and several "also ran" disks, how would you use them?

 

Cheers,

 

Howard

 

[jevans04]

You should include the sizes of the drives you have.

Your largest drive needs to be the parity drive.

[binhex]

if money is no object then i would go with this:-

 

Data and Parity drive

WD Red - these drives are built to be spun up for long periods of time and are quiet, cool and fast too, bit expensive but pretty darn good.

 

cache drive

SSD - performance is the key here, the faster the better thus the selection of SSD, you will need to work out how much stuff you download in a 24 hour period, this will dictate the size of your cache drive, it MAY cost a fair bit to get an SSD that fits the bill if you download a lot, also keep in mind you MIGHT be storing other things on there too, like docker containers, virtual machines, or plugins.

 

if money is an issue then go with:-

 

Data and Parity drive

WD Green - these drives are energy efficient and cost less than the more expensive Red drives, although some people will say the Green drives are not really designed for "always on" devices like servers, they still perform just fine.

 

cache drive

WD Black - cheaper than a SSD and larger size too, but still with fast performance

 

[JonathanM]

So for the gurus:  If you had one WD Red, one WD Black, and several "also ran" disks, how would you use them?

Not nearly enough info if you are asking about drives you already purchased. If you haven't bought anything yet, I agree with binhex. If you already have disks, post exactly which models you have.

[SSD]

For completeness don't forget the HGST (previously Hitachi) disks. They are the most reliable disks based on published studies I have seen and are always my first choice. The are typically cheaper than the Reds too.

 

Also realize that NAS drives are designed for RAID configurations where all drives in the array are often spun up for striped reading and writing. UnRaid's usage patterns vary by user, but are often spun up a very low percentage of their lives - even less, in fact, than most desktops.

[garycase]

Agree that HGST is an excellent choice ... especially since they now have a nice 4TB NAS unit [ http://www.newegg.com/Product/Product.aspx?Item=N82E16822145912 ].    I'd buy a few of those to try instead of the WD Reds I've been using EXCEPT WD has now released a 6TB WD Red, and I won't be buying any more disks as "small" as 4TB 

 

But if you're buying anything up to 4TB, I think the HGSTs, WD Reds, and Seagate NAS units are all good choices.

 

I agree that UnRAID's typical operation is less intense than a traditional NAS unit with regard to the % of time the drives are spun up;  but I still think it's a good idea to use NAS-rated drives.  Not only do they have better vibration control technology than "desktop" drives; but they also have longer warranties.

 

[HDRW]

OK, thanks very much for the advice, folks.

 

I should have mentioned:  I'm planning to use mostly 2TB drives:

 

I already have one 2TB WD "Red", one 2TB WD "Black", one 2TB Seagate 7200.12 as candidates for Parity, and a number of 1TB WD "Blue" (WD10EZEX I think) for data, although I'm not sure if I should start using these and upgrade to larger later, or go with 2TBs to begin with.  If these all seem a bit "small" to some in here:  I don't do much storing of videos - maybe 100GB at the most.  If I fit 4 x 2TB the 6TB data area will last me a good couple of years before space becomes an issue ("famous last words"!).

 

The above drives are all reasonably newly-bought (and unused) but I don't have them to hand to check model numbers.  I'd like to start off with what I have, and only buy others if really necessary.

 

I'm surprised to see SSD being put forward for Cache - since that handles all the writes as they pass through I'd have though it would "wear out" an SSD rather quickly, or have I got this wrong?

 

If I did use the 320GB 2.5" WD Blue (WD3200BEVS) for Cache, would the slower performance of this drive mean it didn't speed things up overall?  (It may also wear out quickly, as it's a laptop drive).

 

Nobody has said definitely: "Use the Red" or "Use the Black" for Parity - does that mean there's not much to choose between them for that job?

 

I didn't mention that I'm in Britain, and getting drives here is nowhere near as easy as in the 'States - we don't have Micro Center or Fry's or anything like them, and prices tend to be a lot higher.  Newegg will ship here, but the higher basic price, shipping, tax etc. mean the $180 drive that garycase pointed to ends up at about $300 over here!

 

Oh, and I never said "money is no object"! 

 

Cheers,

 

Howard

 

[garycase]

Given what you have, I'd use the Black for parity, and the others for data.

 

The 320GB laptop drive is fine for a cache -- it WILL speed up your writes a good bit.

 

Modern SSDs don't have the write cycle issues that they did a few years ago ... using them as a cache isn't an issue at all.    But your laptop drive is fine -- no need to buy an SSD for that.

 

[JonathanM]

I already have one 2TB WD "Red", one 2TB WD "Black", one 2TB Seagate 7200.12 as candidates for Parity, and a number of 1TB WD "Blue" (WD10EZEX I think) for data

Are all of these drives currently empty? Have you run drive tests on them? Unraid relies on all drives being healthy from end to end to enable reconstruction of a single failed drive, so it's a really bad idea to put untested drives into the array.

 

Joe L.'s preclear script is really good for weeding out bad drives, but it will irretrievably erase any data on the target drive.

[SSD]

I agree that UnRAID's typical operation is less intense than a traditional NAS unit with regard to the % of time the drives are spun up;  but I still think it's a good idea to use NAS-rated drives.  Not only do they have better vibration control technology than "desktop" drives; but they also have longer warranties.

 

The NAS drives tend to implement TLER which limits the amount of time a drive may try to take a corrective action on a failure. If it doesn't respond in that timeframe, the RAID subsystem can kick the drive and use other means to deliver the data. But these drives are supposed to limit their error recovery timeframe to let the RAID (NAS) do its own data recovery.

 

UnRaid doesn't use TLER so this feature is not necessary in the drives. There may be some advantage of allowing a drive to do its best to try to recover, and not return as soon as possible.

 

Certainly longer warranties and better quality are reasons that one might want to purchase these drives, but their NAS designation is advertising a feature you don't need for unRaid.

[darkside40]

Before opening a new thread for my question i will use that one here because it is leading in the same direction.

 

I am also searching new 3TB drives to exchange my 3 year old 2 TB Hitachi drive step by step. But my Server is not running 24/7. The drives are spun down after 15 min of inactivity.

 

Would it be better for me to use the WD Red drives or would it be more clever to use the standard desktop drives because they are not made for continuous use and could handle the start and stop better?

[itimpi]

Before opening a new thread for my question i will use that one here because it is leading in the same direction.

 

I am also searching new 3TB drives to exchange my 3 year old 2 TB Hitachi drive step by step. But my Server is not running 24/7. The drives are spun down after 15 min of inactivity.

 

Would it be better for me to use the WD Red drives or would it be more clever to use the standard desktop drives because they are not made for continuous use and could handle the start and stop better?

In my experience it makes little difference, they both perform well with unRAID.  I have traditionally used Green drives, but as the drives have got larger have been tending to use the Red model.  In particular I recently got my first 6TB drive and went for the Red model because it is currently more generally available; the price premium is small; and I like the longer warranty period.

 

One question - you talk about exchanging a 2TB drive for a 3TB one?    Is this as a result of failure or as part of an upgrade.  I would not have thought upgrading a 2TB to a 3TB was a cost effective upgrade any more unless you already have the drive.  I would think that 4TB was a more cost effective upgrade, and 6TB should be considered (although since you have to upgrade both parity and a data drive you may decide that is step to far at this point).

[darkside40]

No that was no failure. I have upgraded my parity drive last year to a 3TB Seagate drive with 7200rpm. I have still 600GB free on my array and the amount of data is not growing so fast in my case. So when i switch all my drives from 2TB to 3TB the resulting 15TB will last for the next couple of years.

 

[itimpi]

No that was no failure. I have upgraded my parity drive last year to a 3TB Seagate drive with 7200rpm. I have still 600GB free on my array and the amount of data is not growing so fast in my case. So when i switch all my drives from 2TB to 3TB the resulting 15TB will last for the next couple of years.

I would still think it was likely to be cost effective to get a new 4TB disk and make that your new parity drive with the old 3TB parity drive becoming a data disk.  That will position you well for the future as you can then use 4TB drives for any further upgrades if you have underestimated that data growth.

[SSD]

I do not think it is an emergency to replace the 2T drives. I have a bunch of them in my backup array, and also a bunch of 1T drives, and even a few 750G drives. These drives are all working fine. I check thier smart attributes and run parity checks. An incremental upgrade strategy is needed.

 

The following is based on the following price assumptions

3T - $99 ($33/T)

4T - $140 ($35/T)

6T - $289 ($48/T)

 

Buying a 3T to replace a 2T costs $99 per T. For 15 drives the cost is $1485 ($99/T)

 

Buying a 4T to replace a 2T costs $70 per T. To move up to 4T you would need a larger parity. So if you bought 2 4T drives (one for parity and one for data, using your existing parity for data) you would spend $280 and net 3T of space ($93/T). But going forward your cost would be $70/T as you upgrade each disk. For the extra 15T, the cost would be $1119 ($74.6 per T)

 

Buying a 6T to replace a 2T costs $72.25/T. Like with the 4T, you would need a larger parity. Buying 2 6T drives would net 5T of space ($116/T). But going forward the cost would be $72.25/T. For the extra 15T, the cost would be $1302.50 ($87/T)

 

This doesn't take into account the expected cost reductions (especially on the 6T drives) expected over time. And there is a hybrid model of starting to buy 4T drives and then switching over the 6T drives once the prices drop a bit more. The other thing it doesn't account for, is that after you fill up with 3T drives your array is 15T larger, and then you need to start swapping them out to grow. Whereas with the 4T the size would be 30T larger, and with the 6T drives your array would be 60T larger. It will take a much longer time for you to outgrow the space!

 

I do caution that the 6T drives are very new and there is little reliability data compared to the 3T and 4T models. But as users start to buy them we should start to learn more about their failure rates.

 

It's up to you, but I would never buy another 3T drive for your array. I'd probably first buy a pair of 4T drives, and after that is used up start with the 6Ts. Or just bite the bullet and go with the 6T.

 

(Double check my math before taking this as gospel!)

[garycase]

I'd look at it a bit differently.

 

You can't buy a selected number of TB's at the cost/TB outlined above, so I'd simply look at the net outcomes of (a) staying with 3TB drives;  (b) using 4TB drives; or © using 6TB drives.

 

First, since you server only has 6 drives in it, I'll use numbers that actually match your system 

 

Assuming you goal is to add 5 TB to your capacity (changing it from 10TB to 15TB), then you can do this by either (a) buying 5 3TB drives and keeping your current parity drive (cost = $495);  (b)  buying a 4TB parity, swapping one of your 2TB drives with the current parity, and buying 2 more 4TB drives  (cost = $420);  or ©  buying a 6TB parity, swapping one of your 2TB drives with the current parity, and buying one more 6TB drive  (cost = $578).

 

Note, however, that there are additional factors you should consider:

 

Option (a) would have no further expansion capability without further drive replacements.

 

Option (b) would have 4TB of additional expansion capability (2 more drives) if you only replace the remaining 2TB drives ... or 5TB if you also replaced the 3TB drive.

 

Option © would have 12TB of additional expansion capability (3 more drives) if you only replace the remaining 2TB drives ... or 15TB if you also replaced the 3TB drive.

 

Note also that I think the cost assumptions bjp999 used are a bit low for both the 3TB and 4TB choices.    Best price I see today for a 3TB Red is $122;  for a 4TB it's  $172.  The 6TB pricing is good ... in fact, I found it for $279.    But leaving the 6TB price as is, if you use the $122 and $172 pricing for the 3 & 4 TB units, the costs are $610 for option (a);  $516 for option (b);  and option © is unchanged at $578.

 

Clearly the numbers vary a bit depending on which drives you choose to buy -- but the last cost figures are all "apples to apples" -- with all drives involved being WD Reds.

 

But for the nominal cost difference, I'd go with option ©, as it's actually LESS expensive than option (a) to add the same amount of storage; only $62 more than option (b); and has FAR more expansion capability in the future.

 

[SSD]

I recently saw 3T drives (HGST I think) on sale for $99. I am not exclusive to the WD Red. I think I misunderstood the number of drives in the array in my analysis but you get the idea.

 

With a smaller array I believe that larger drives make sense even paying a moderate premium because, in the longer term, you will be forced to swap out drives less often. The most expensive space we buy is upgrading drives because we need more space and have no more slots.

[garycase]

I didn't mean to imply that you couldn't find drives for those prices ... only that they're lower than what you can usually find them for.    I also felt that when comparing costs, it was fairest to use the same make/model for all the drives ... I used pricing for WD Reds; but it'd also be fine to do the same calculation for WD Greens; HDST drives; Seagate NAS units; etc.  (although HGST doesn't yet have a 6TB unit to include in the mix except for the very costly helium-filled unit).

 

I deduced the number of drives in the system from the comment "... So when i switch all my drives from 2TB to 3TB the resulting 15TB will last for the next couple of years."  ==> which clearly implies a total of 5 data drives plus parity.

 

[SSD]

I didn't mean to imply that you couldn't find drives for those prices ... only that they're lower than what you can usually find them for.    I also felt that when comparing costs, it was fairest to use the same make/model for all the drives ... I used pricing for WD Reds; but it'd also be fine to do the same calculation for WD Greens; HDST drives; Seagate NAS units; etc.  (although HGST doesn't yet have a 6TB unit to include in the mix except for the very costly helium-filled unit).

 

I deduced the number of drives in the system from the comment "... So when i switch all my drives from 2TB to 3TB the resulting 15TB will last for the next couple of years."  ==> which clearly implies a total of 5 data drives plus parity.

 

And I deduced that the 15T was the extra space he would get after the 1T upgrade on each drive since whatever he had was all used up. But you could be right.