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Expanding Raid5 Array in Windows 7

I

izusaga

Limp Gawd
Joined
Oct 4, 2005
Messages
475
I need to expand a Raid5 array on an Intel Z77 from 4 to 5 HDD's. Two questions:

1) Will the expansion require a full initialization? The Raid5 with just 4 drives took about 6 days to fully initialize, so I'm afraid of what all 5 would be.

2) Is there any actual detriment to performance from an expansion of the array? Or should I just rebuild entirely?

Gratzi,
Izu
 
If you open Intel RST with the 5th drive in, does it show expansion of the array is even possible? Or are you using Windows RAID or another type of controller?

Anyways, welcome to the world of RAID 5.
 
bigdogchris said:
If you open Intel RST with the 5th drive in, does it show expansion of the array is even possible? Or are you using Windows RAID or another type of controller?

Anyways, welcome to the world of RAID 5.
Click to expand...

The array has no data on it - but after spending 6 days initializing I dread doing it all over again after adding the 5th if I have to do a full re-initialization, which is the primary reason I'm looking to expand - I need to access this drive ASAP as the NAS it is replacing is in predictive failure status and the only way to fix that is dropping $400+ on a drive I won't use long-term.

RST shows the ability to expand the array. I just need to know if it will do a full initialization once I expand the 5th drive in.. if so, I might as well just break the array and re-create from scratch - essentially I am looking to initialize the array the fastest way possible without impacting performance at all (IE does expansion create any performance issues I should be aware of?). Make sense, or am I off here?

Thanks!
 
Wow it really takes 6 days to initialize an empty raid array? Sounds seriously crappy...
 
danswartz said:
Wow it really takes 6 days to initialize an empty raid array? Sounds seriously crappy...
Click to expand...

4x 3TB consumer-grade HD's are not race cars. ;) But once initialized they serve my needs of up to 8 simotaneous streams @ approximately 400mb/s read/write.

I'm sure a dedicated hardware raid controller would initialize faster, but honestly there would be no noticeable performance gain from doing so, so it doesn't justify the $300-400 cost of a controller able to handle 5 drives.
 
I am by no means a RAID expert but if you expanded the array I would expect the entire array would need to be rebuilt, mainly due to the parity. A total rebuild would probably mean another initialize to verify.

According to a post on Intel's forums, enabling Write-Back Cache can help the performance of Intel integrated RAID 5.
 
Oh sigh. I forgot this is HW raid - it doesn't know what if anything is actually in use...
 
bigdogchris said:
I am by no means a RAID expert but if you expanded the array I would expect the entire array would need to be rebuilt, mainly due to the parity. A total rebuild would probably mean another initialize to verify.

According to a post on Intel's forums, enabling Write-Back Cache can help the performance of Intel integrated RAID 5.
Click to expand...

Since this NAS is connected to a UPS, this would probably be an intelligent idea. Totally forgot about checking this - thanks!

danswartz said:
Oh sigh. I forgot this is HW raid - it doesn't know what if anything is actually in use...
Click to expand...

Mind clarifying specifically what that entails for me?
 
izusaga said:
Mind clarifying specifically what that entails for me?
Click to expand...

I use ZFS, and since it is software raid and filesystem all in one, it knows which blocks are in use, so creating a raid array is basically instantaneous. If you are running a HW raid card, this doesn't relate to you.
 
danswartz said:
I use ZFS, and since it is software raid and filesystem all in one, it knows which blocks are in use, so creating a raid array is basically instantaneous. If you are running a HW raid card, this doesn't relate to you.
Click to expand...

The array is created instantly - the parity initialization is what takes a long time. I'd imagine this would be less of an issue if we weren't talking about 12TB of data.
 
izusaga said:
4x 3TB consumer-grade HD's are not race cars. ;) But once initialized they serve my needs of up to 8 simotaneous streams @ approximately 400mb/s read/write.

I'm sure a dedicated hardware raid controller would initialize faster, but honestly there would be no noticeable performance gain from doing so, so it doesn't justify the $300-400 cost of a controller able to handle 5 drives.
Click to expand...

The drives aren't the problem, I can initialize a 16 x 3TB Drives in RAID6 with an Areca in not much more time than it takes to zero fill an individual 3TB drive - 6 or 7 hours. The problem is either the peashooter chip thats handling raid functions on that board (I'm not up to date on what Intel's done w/ the controller on the Z77 boards) or theres a setting wrong somewhere like write back cache not being enabled as someone mentioned, or all of the above.

And FWIW the "no noticeable performance gain" with hardware raid isn't accurate -- what you gain with hardware raid is minimizing the window that your data is exposed to data loss in the event of a drive failure by rebuilding in a matter of hours rather than days. But I'm hoping for your sake there's just an incorrect setting, because that just doesn't sound right. Then again nothing surprises me with desktop class motherboards because motherboard competition is fierce and its all about keeping costs down, combined with the fact 99.x% of people buying these boards won't use the RAID5 functionality so manufacturers aren't compelled to outfit a solution with more parity calculation muscle, which would only add to cost.

Also, there are multiple types of initialization and what's offered depends on the controller but it boils down to background and foreground initialization. background means the logical volume is available immediately to the O/S while the controller continues the initialization in the background. this normally takes a long longer than foreground, which doesn't make the LV available until init is complete. I ALWAYS go foreground init because its the easiest on the drives and controller. So see if thats an option at the init step.
 
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izusaga said:
The array is created instantly - the parity initialization is what takes a long time. I'd imagine this would be less of an issue if we weren't talking about 12TB of data.
Click to expand...

this is semantic quibbling. in my book the array isn't created (and therefore usable) until the parity is all calculated and written.
 
danswartz said:
this is semantic quibbling. in my book the array isn't created (and therefore usable) until the parity is all calculated and written.
Click to expand...

I agree. I for the most part do not use an array until it has finished initialization. However on a 2008 quad core or better system + linux software raid6 initialization takes hours not days. For example an 10 drive (hitachi 7k2000) x 2TB raid 6 array on a core2quad took less than 9 hours on a core2quad q9550 at work.
 
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With all this being said - I'm open to software raid suggestions. The only caveat being for my purposes my NAS has to run on Windows 7 (since it serves multiple purposes that require a Windows OS on my network and for my current streaming simplicity). Since I'm adding the 5th 3TB drive today, I have the opportunity to try a product.. but I need to ensure it's reliable enough that my data is not at risk in the event of hardware failure outside the drives, etc.. right now I can swap any Z77 board in and it will work fine with the array once it's configured.
 
Personally, I'd just drop a PERC 6/i in there and run the drives off of that. But that's me, and I've been running both of my PERCs for years - and LOVE them.
 
Software raid zfs allows you to use your raid and load it with data, immediately after creation. No need to wait more than one second.

With that said, zfs is not for you because you can not easily change the number of disks in à zfs raid after creation. The number of disks is fixed. You seem to have à need of changing nr of disks, after raid creation.
 
The only option for you is to get RAID card in there and call it a day. If Windows is the requirement then that's the only option I can think of. I'll use onboard / fake-raid for usually RAID 1.. maybe RAID 0 if there's a need. Anything larger than that though i'll use hardware raid for a whole host of reasons.

Hmm there's one other option... software raid. These would be Flex RAID or Snap RAID.
 
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