I've been reading some of the threads / wiki entries regarding the "green power" WD drives. I'm left in a quandary..

My current unRAID spec is:

* Motherboard: Asus P5B-VM DO

* Processor: Intel Celeron 440 2.00GHz Socket 775 FSB800

* RAM: Kingston 2x512MB DDR2 800MHz/PC2-6400

* Hard Drives: 3x Western Digital WD1000 1TB RE2 Green Power drives

 

As soon as i can find an affordable SATA backplane i'm going to add another 1TB drive and a couple of 500gig drives (which i have lying around), as well as upgrading to the top unRAID package (professional?).

 

My worry is, i'm using one of the green power drives for parity, i'd prefer to buy another identical drive for consistency, but if i'd get better performance by swapping the green power drive for a faster parity drive.. that might be better. Then i can just use the old parity drive as my expansion.

 

I'm also wondering how easy it is to swap my parity drive over!

 

Thanks in advance guys.

To replace the parity drive, stop the array, power down, swap in the new drive, power back up, press "Start"

 

More detailed instructions here, but they basically say the same: http://lime-technology.com/wiki/index.php?title=UnRAID_Manual#Replace_a_single_disk_with_a_bigger_one

You may get slightly better performance with a 7200 RPM parity drive, but likely won't be very noticable. Others have reported good results with GP parity drives.

My performance did not change much with the 7200RPM parity drive and a 5400RPM data drive.

The extra ram does help, but in the end you can still only move so much data to the system without incurring a penalty.

I found with rsync and bwlimit I would max around 13-15MB/s before I started hitting those mega pauses while the cache was being fliushed. Without bwlimit I would burst at over 30MB/s but then come to a screeching halt as parity updates took place.

I'm sure if I had a 7200RPM data drive the performance would be slightly better, but I doubt by much during writes.

Okay, seems that i have nothing to worry about with my current spec.. But if you were me, and you were going to be buying another one or more TB drives soon, would you just stick to the same drive, or buy a 7200rpm drive to replace the parity, just because you could?

would you just stick to the same drive, or buy a 7200rpm drive to replace the parity, just because you could?

 

I did put in a Seagate 7200 RPM drive for the Parity drive, mostly because the price was at the same price point as the WD green drive and it had the larger 32MB cache.

The performance increase was not that noticeable. What was noticeable was the increase in ram

From how much RAM to how much?

I'm thinking about going from 1gig to 2gig now that unRAID supports it.

2GB is usually enough, it helps with keeping directory entries in ram.

There are some kernel tunings to help with that.

 

If you can afford it, go to the full 4GB, which will probably yield 3.2 to 3.5GB of available ram.

More then that will be moot unless it is a heavily used system.

There are plenty of rebate offers on newegg to offset the costs.

Generally I've been paying about $60 for 4GB since January.

My environment is 8GB with PAE enabled in the kernel.

Then again I'm installing allot of packages and using the system in an unconventional manner.

I'd probably move a Seagate 7200RPM drive in place of the WD 5400RPM parity drive, but would not expect miracles.  But even a small performance boost is likely worth the effort IMO.  Otherwise I'd always be wondering if it would make a difference.  I'd suggest running a full parity check before trying the swap.  The reasons are documented in the wiki (click "Best of Forums" link in my sig, and read posts in the "Maintenance Recommendations" section).

 

I run 2G of RAM and get good performance.  No amount of RAM is going to speed up your disks, but more memory can be used creatively as WeeboTech has done.