Author Topic: Questions about PPU Drive and Selection of Components  (Read 2877 times)

Offline stang725

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Questions about PPU Drive and Selection of Components
« on: October 10, 2011, 05:32:34 pm »
Will I see any performance benefit to using a faster PPU Drive.

Will have 4 2TB WD Green 5400's for DRU

Was either going to use another 5400, or a 7200 for PPU....  if there will be a performance boost for write operations using a faster drive.

Using Freenas right now, want to run under win7 for ease of U/I and better driver support.

Any sage advice or lessons learned would be much appreciated.

My build:
GIGABYTE GA-Z68A-D3H-B3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard w/ Intel PCI Gigabit NIC
Intel Pentium G620 Sandy Bridge 2.6GHz LGA 1155 65W Dual-Core
G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) (might put in another 8gig down the road)

OCZ Vertex 3 VTX3-25SAT3-60G 2.5" 60GB SATA III MLC Internal Solid State Drive (SSD) to onboard SATA 6Gb/s for WIN7 OS
(4) Western Digital Caviar Green WD20EARS 2TB 64MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive to onboard SATA 3Gb/s for DRUs
(1) TBD PPU Drive to onboard SATA 6Gb/s

All parts will be bought once I finalize my selections, so open to recommendations, other than the 4 Green drives that I already have. Will also use computer for occasional win7 tasks related to torrents, newgroup d/l, and stripping of video from bluray images to mkv(no conversion).

This NAS will serve 4+ computers for basic filesharing and will need to be able to stream 1080p DTS mkv to 2 computers simultaneously. My current build w/ just the 4 WD greens is able to support this using FreeNAS in ZFS (RAID-5) type config, at least as far as disk/network I/O is concerned....

So my only concern is really the benefit of using a faster PPU drive and the amount of memory I will need to support a stripped down win7 install and the Flexraid engine. Well, I guess my other concern would be execution of said build/install and learning how to recover a lost drive.... something I taught myself how to do in FreeNAS and now a year later would prob have to spend a day or two reading forum entries before I would even be able to attempt a recovery.... hoping that flexraid will be alittle more intuitive then FreeBSD CLI.

Offline stang725

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Re: Questions about PPU Drive and Selection of Components
« Reply #1 on: October 10, 2011, 05:39:40 pm »
Oh, and any advice for engine selection would be very helpful as well.

Offline xliv

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Re: Questions about PPU Drive and Selection of Components
« Reply #2 on: October 11, 2011, 05:10:16 am »
Server HW: ASUS P8B-E/4L + PIKE 2008 SAS | Xeon E3-1230 | 8GB DDR3 ECC 1333 [Kingston - KVR1333D3E9SK2/8G] | Intel 320 - 80 Go (OS)
Server OS: Win7 64b EN
FlexRAID 2.0 latest build, Cruise Control, 7 DRUs (6x3TB,1x2TB), 1 PPU (2x2TB)

Offline stang725

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Re: Questions about PPU Drive and Selection of Components
« Reply #3 on: October 11, 2011, 11:08:30 am »
So T1+ would prob be the best choice, given that I only need/want one PPU..... Any ideas on the benefit of using a faster PPU drive than the DRUs.... I would think it wouldn't, but I don't know enough about the engine to be confident and I figured someone here might... Thanks

Offline someone

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Re: Questions about PPU Drive and Selection of Components
« Reply #4 on: October 11, 2011, 09:20:13 pm »
Haven't read the wiki, but in my personal opinion if you are going to have more than 4DRU, I would recommend 2PPU simply because I seethat you can afford to do so.
As far as 7200RPM vs 5400RPM, I would go with 5400 but that's specifically in your case.  As for myself I prefer quiet and low power PC.  But in your case, as long as your new HD is SATA3, the benefit of that alone will be greater since all your DRUs will be in SATA2 anyway.  I mean you can't be writing much faster than reading anyway, considering the nature of the RAID, read>make-parity>write.  So, reading off the old drive will probably be your bottle neck here.  Also, since your PPU have to be the same size or larger, you will have to either get 2TB or 3TB drive.  In the latter case you are looking at speed gain by data density compared to former.  Of course data density may lead to other problem but so far not much data is known about such high data density HDD.  So make yourown choice.

Offline t-lor

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Re: Questions about PPU Drive and Selection of Components
« Reply #5 on: October 12, 2011, 03:14:42 am »
Haven't read the wiki, but in my personal opinion if you are going to have more than 4DRU, I would recommend 2PPU simply because I seethat you can afford to do so.
in my personal opinion, the chance of 2 drives failing at the same time aint that big, so 1 would do.
But you do gain some security by adding a second DRU.
I gues its down to how much u spend, and how much security u need.
IMHO that second drive would be better spend as an ofline backup of the really important bits :)

Quote
But in your case, as long as your new HD is SATA3, the benefit of that alone will be greater since all your DRUs will be in SATA2 anyway. 
just for the record, the only benefit speedwise is the maximum bandwith of the connection to the drive.
Since SATA2 goes to 300MB/s, theres really no drive yet that even comes close to that speed !
So there's no difference between sata2 and sata3 drives !

Offline someone

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Re: Questions about PPU Drive and Selection of Components
« Reply #6 on: October 12, 2011, 03:58:26 am »
in my personal opinion, the chance of 2 drives failing at the same time aint that big, so 1 would do.
But you do gain some security by adding a second DRU.
I gues its down to how much u spend, and how much security u need.
IMHO that second drive would be better spend as an ofline backup of the really important bits :)
I know what you are thinking, but I think you seem to make the same mistake as other people.  Unlike Live RAID, FR isn't a protection against drive failure, but data failure.  And data failure <> harddrive failure.  It only take a fail harddrive and some damage/modified files on another drive to start ruining your restoration.  And yes you can do that live mode in FR, but I don't think that's how people view FR, at least not the main function.  And I would imagine the performance of Live mode in FR wouldn't be that spectacular.

just for the record, the only benefit speedwise is the maximum bandwith of the connection to the drive.
Since SATA2 goes to 300MB/s, theres really no drive yet that even comes close to that speed !
So there's no difference between sata2 and sata3 drives !
You are right, I forgot about that.  But are you sure you won't gain any benefit at all?  I mean it's true that even SATA3 harddrive would never hit SATA2 bandwidth limitation, but I just have to wonder since SATA3 would be newer model, would you gain some slight performance just because it's a newer model or other features that didn't exist in SATA2 model?

Offline jasonwc

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Re: Questions about PPU Drive and Selection of Components
« Reply #7 on: October 12, 2011, 10:45:28 am »
SATA 3 provides no benefit over SATA 2 for mechanical drives. It was designed for, and is very useful for the new SSDs that can do 500 MB/sec+. The fastest consumer 7200 RPM mechanical drives can only do around 150 MB/sec and that is at the outer edge of the spindle. Once you get closer in, speeds fall. The only area where SATA 3 is theoretically faster is access to the 32/64 MB cache, but this has almost zero impact for large file transfers.

However, newer drives ARE faster than older drives because they have higher density platters. So the newer SATA 3 drives are likely faster than older SATA 2 drives simply because of higher aerial density. Even if the drives are the same capacity, newer drives often have fewer spindles.

In addition, the SAS 2.0 controllers which support SATA 3 are likely faster than the older SAS 1.0 controllers/SATA 2 because of updated designs. While you theoretically get 300 MB/port on a SATA 2 controller, most controllers can't provide such speeds if all drives are being read simultaneously which is the way that FlexRAID operates. Newer controllers will provide better performance than older controllers, generally.  For example, you should get higher aggregate speeds while doing a build or verify process with the AOC-SASLP2-MV8 than the original AOC-SASLP-MV8. The new controllers are just faster and can push more data.

So,  a SATA III controller or drive isn't faster because of the interface, but it's probably still marginally faster.
« Last Edit: October 15, 2011, 12:32:33 pm by jasonwc »
Norco RPC-4224 4U Rackmount Case (24 Hotswap Bays) | Asus P8B Workstation Motherboard (four PCI-E 16x slots @ 8x/8x/4x/4x and dual 82574L Intel server NICs) | Core i3-2100 | Supermicro AOC-SASLP-MV8 SAS Controller | Corsair TX650v2 PSU | Currently 16 TB array, 2 TB parity | WHS 2011

Offline stang725

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Re: Questions about PPU Drive and Selection of Components
« Reply #8 on: October 15, 2011, 08:43:31 am »
Yeh, SATA3 isn't really going to shine with a mechanical drive.... Need a SSD for that.. But really my question was more geared toward whether or not the Parity drive, the PPU will allow for a faster initial build or for parity updates if it is notably faster in terms of I/O than the DRUs, since it will be reading from the 4 other drives simultaneously(I think).... I guess I need to ready up some more on how it creates the snapshots of parity.