Hello

I´m looking for a 2TB parity drive.....Black friday is coming with good price, but lot of the good deals are based on "Green" or "LP" disks, meaning 5,400 or 5,900 RPM

Do I really need a 7,20 rpm drive for the parity disk, or not?

Thanks

 

No, you don't need a 7200 rpm drive.  The only circumstance in which I would recommend a 7200 rpm drive for a parity drive is if you have a high number of other 7200 rpm drives in your server.  If you don't, then get a green parity drive.  Remember that a data transfer is only as fast as the slowest drive involved (so a fast parity drive and a slow data drive will still result in a slow transfer speed).

 

The other thing to watch out for is to not buy a Samsung F4 as they are currently incompatible with unRAID.  And remember to jumper your WD EARS drives....

Im really new at this but seems to me like the better option for write speed would be a fast cache drive, if you feel ok with having your data unprotected for a while (at leas until the data is copied to the array)

I have 2 x Seagate Barracuda 1.5TB at 5,900 rpm, and 1 x WD EADS 1.5TB (not sure about the speed though)

Should I look for a 7,200 rpm parity drive, or a 5,900 will be good enough

I can also install a cache disk (250Gb – 7,200 rpm) that I already own

 

Thanks

 

The write speeds to the protected array will be limited by your slowest drive.

 

The only times a faster parity than data drive will help is if you have multiple concurrent writes to the array. That is where the faster parity drive speed can help out.

 

If you're not looking to use 7200 rpm drives in the near future and you don't do heavy concurrent writes to the array, then you have no need for a 7200rpm or faster parity drive.

Do you even need an unRAID array?

 

Your question asks if you need a 7200rpm drive for parity. The answer is no, you do not need one. You may want one though.

 

A 7200rpm drive might make any writes a little quicker if you perform writes from 2 different machines to 2 different unRAID disks at the time. Otherwise, don't worry about it.

 

The WD Green drives have been working fine as parity for me.

 

Peter

 

I have four 1.5tb 7200rpm drive in my array now and want to add another. But I would like to jump up to 2tb drives from here out so I would be replacing the parity drive with a new 2tb drive.

 

So the only time performance would be effected is when writing to one of the 1.5tb drive correct? If I add more 2tb drive down the road they would be 5900 rpm also. Read speed is not effected at all?

 

Also what is really the limiting factor here, I would have thought that the gigabit network would be slower then the drive speed any way isn't it? Nother works then I copy files from a windows maching over gigabit would I notice a diffrence from a 5900 to 7200 drive?

I have four 1.5tb 7200rpm drive in my array now and want to add another. But I would like to jump up to 2tb drives from here out so I would be replacing the parity drive with a new 2tb drive.

 

So the only time performance would be effected is when writing to one of the 1.5tb drive correct?

If you place the 7200 RPM parity drive with a 5900 RPM drive, it will affect when you write to ANY drive that is faster than 5900 RPM. (In other words all of your current 7200 RPM drives).  The SLOWEST drive determines the write speed of the array when writing to a single disk.

If I add more 2tb drive down the road they would be 5900 rpm also.

Since they are the same speed as the parity drive they will not be slowed down additionally.

Read speed is not effected at all?

Correct.

Also what is really the limiting factor here, I would have thought that the gigabit network would be slower then the drive speed any way isn't it?

No, rotational speed is the bottleneck.  To write a single sector, it must first be read from BOTH disks (parity and data) then written to both disks.  The disk must rotate to get the same sector under the read/write heads in between.  Then they must rotate once more to get to read the next sector written.    A rough guide is to figure 2.8 revolutions of the disk is needed to write to a single sector.    If you revolve faster, you write faster.

Nother works then I copy files from a windows maching over gigabit would I notice a diffrence from a 5900 to 7200 drive?

You might notice a difference.  7200 RPM drives can get 35-40 MB/s.  5900 RPM drives typically can be written to at 25-35 MB/s.

I have found for my Seagate LP 2TB parity drive, that writes to my faster 7200rpm drives go at 35+ MB/s, sometimes touching 40 MB/s, while writes to my "green" drives go at about 25-30 MB/s.

 

But really, if you're running unRAID as a media server, it's all pretty moot. If you write 100 GB at 25 MB/s, it will take about 68 minutes. 100 GB at 40 MB/s will take about 43 minutes. In either case, you can walk away and do something else.

"The other thing to watch out for is to not buy a Samsung F4 as they are currently incompatible with unRAID" is not a true statement.

 

I have 3 in an unRaid at present and they are 100% compatible. They are not an ideal choice as a parity drive since they suffer the write penalty due to being an advance format drive, however the statement makes people who already have them feel like they can break at any time. As a large format storage drive (movies, tv shows etc...) there is no difference between them and any other drive as their writes to the drive are still 35-40 MB/s (without a cache drive), and their read speed is not affected.

 

The statement should be "Samsung f4's are not an ideal choice for a parity drive or storing small files due to write performance."

 

If you install the cache disk then it wont really matter at all. A good cache drive with current hardware can see 50-70 MB/s. The only place it will matter is your Parity checks and as Kenoka said "If you write 100 GB at 25 MB/s, it will take about 68 minutes. 100 GB at 40 MB/s will take about 43 minutes. In either case, you can walk away and do something else."

Coincidentally, I just had to do a hard reboot, and am in the midst of a parity check. At 1.2% done, I'm getting estimated speeds of over 80 MB/s. It peaks at close to 90 MB/s, and seems to hover in the 85-88 MB/s range most of the time. In the time it's taken to write this, it's gone to 2% done.

 

So it's about 7 hours for a full parity check, which is not bad, as far as I'm concerned, especially since you can still read data while it's going.

Are the Seagate on sale on Newegg at $69.99 a good choice for parity drive? Reviews are average, and lot of people say they fail after few months.....

Hard Drives are almost entirely a matter of preference. You go with what's cheapest till you get burned by one, then you tend to avoid that manufacturer till another one burns you. Then the cycle resets.

 

I personally had too many 1.5 TB Seagates die on me (4 to be exact) to go back to them just yet.

 

It is really cheap for a lot of storage. Has a 5 year warranty.

 

Spec and performance wise it is a perfectly acceptable parity disk. I am sure there are many people on here using them.

 

At some point all hard drives will stop working, just hope that point is not when you are still using it.

IIRC, Seagate LP drives have a 3 year warranty.

I have really liked mine so far. I was worried about the reports of noise, but mine has been so quiet I can't even hear it. It runs cooler than my WD EADS drives. I chose it because it gets better performance than the WD Green, and draws less power at idle. For the price, I don't think you can go wrong.

 

Edit: i just pulled the trigger on another one of these to act as a warm spare/cache drive.

I know the box said 3, but the site said 5 year. If that's true then I really won't buy one now. 

Seagate's site states:

The SATA 6Gb/s interface and 64MB cache maximize performance.

so I think they may be upgrading the specs on this drive.

 

They also state:

Barracuda® Green drives from Seagate save you time. Available now with SATA 6Gb/s interface and 64MB cache and combined with the industry's only 5900-RPM spin speed, you can be sure you're getting the best performance in the green-power drive category.

 

Seagate SmartAlign™ technology simplifies your transition to the Advanced Format (AF), 4K standard. There is no need for time-consuming integration utilities required by similar AF drives.