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Some questions about RAID.

post #1 of 2
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So I'm a newbie to RAID configurations, but I'm considering setting one up for my i7 build. My first thought was to put two Caviar Blacks in RAID 0 to increase their performance. After reading more reviews, posts, and opinions on HDDs, I'm starting to get paranoid about losing drives, so I'm considering getting a third Caviar and going with a RAID 5 setup to include parity and allow the loss of one drive.

So my questions:

1) If you set up a RAID array with 2 drives (say I put 2 Caviars in RAID 0), can you change the RAID array (say I want to take those 2 out of RAID 0 and putting them into RAID 1)? Do you simply need to format the drives and change the RAID settings in the bios?

2) How would 3 drives in RAID 5 perform in comparison to two drives in RAID 0? I assume that the parity is going to slow down writing processes, but will the third drive increase read performance?

3) I've been reading around a little bit and I keep coming across talk of hardware vs. software controlled RAID. Are RAID arrays set up through the motherboard hardware driven? I assume a software array would be set up with some kind of third party program via the OS. Am I on the right track there?
post #2 of 2
Quote:
Originally Posted by constantkube View Post
1) If you set up a RAID array with 2 drives (say I put 2 Caviars in RAID 0), can you change the RAID array (say I want to take those 2 out of RAID 0 and putting them into RAID 1)? Do you simply need to format the drives and change the RAID settings in the bios?
You would need to format the drives - change the setting in the RAID setup from striped (RAID 0) to mirrored (RAID 1). Then reinstall the OS.

Quote:
Originally Posted by constantkube View Post
2) How would 3 drives in RAID 5 perform in comparison to two drives in RAID 0? I assume that the parity is going to slow down writing processes, but will the third drive increase read performance?
From wikipedia:

Quote:
RAID 5 implementations suffer from poor performance when faced with a workload which includes many writes which are smaller than the capacity of a single stripe;[citation needed] this is because parity must be updated on each write, requiring read-modify-write sequences for both the data block and the parity block. More complex implementations may include a non-volatile write back cache to reduce the performance impact of incremental parity updates.

Random write performance is poor, especially at high concurrency levels common in large multi-user databases. The read-modify-write cycle requirement of RAID 5's parity implementation penalizes random writes by as much as an order of magnitude compared to RAID 0
Simple solution - for performance go with RAID 0 or RAID 0+1 for performance with backup.

Quote:
Originally Posted by constantkube View Post
3) I've been reading around a little bit and I keep coming across talk of hardware vs. software controlled RAID. Are RAID arrays set up through the motherboard hardware driven? I assume a software array would be set up with some kind of third party program via the OS. Am I on the right track there?
There are three ways of setting up a RAID array.

1). Software based (I'm not too familiar with those but from what i've heard there can be a lot of problems with software RAID arrays)

2). Host / Firmware Based

A host-based controller loads firmware upon startup - this controlls the RAID array until the OS boots up and the drivers for the controller are used. This is a cheap solution and gives better performance than software RAID but most processing is done by the motherboard/cpu (hence the name 'host controller' - the host does the majority of the work) Onboard RAID 'controllers' that are included on a motherboard chipset are host-based Host based PCIx cards range from $10 - $60

3). Hardware Based

By far the highest performing, most stable and most expensive solution. The RAID controller is a standalone controller that controlls the array the whole time. They're pretty much their own little computers which do nothing but control the RAID array. They can have onboard memory and battery backups to prevent data and settings losses. They are also the most expensive. Prices range anywhere from $85 - $650+

Good Luck
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Simply Green
(24 items)
 
NAS
(11 items)
 
CPUMotherboardGraphicsGraphics
Core i5 4670k Gigabyte G1.Sniper Z87 - ATX - LGA 1150 Zotac GeForce GTX 760 2GB Zotac GeForce GTX 760 2GB 
RAMHard DriveHard DriveCooling
G.Skill Sniper 8GB (2 x 4GB) DDR3-1600 Memory  Samsung 840 EVO 120GB 2.5" Solid State Disk Samsung 850 EVO 120GB 2.5" Solid State Disk EK-Supreme LTX - Nickel CSQ 
CoolingCoolingCoolingCooling
XSPC RX 360 Monsoon Hardline Economy Fittings - Matte Black Bitspower Rotary 90 Degree Fittings - Matte Black NoiseBlocker Black Silent Pro PLPS PWM 120mm (Q... 
CoolingCoolingCoolingCooling
Aquacomputer Aquaero 5 LT EK D5 Vario Pump with X-Top Bitspower Water Tank Z-Multi 150 V2 1/2" x 3/8" PETG Rigid tubing 
CoolingCoolingCoolingCooling
EK-FC670 GTX (Qty 2) EK-FC670 GTX Backplate - Black (Qty 2) EK-FC Bridge DUAL Parallel 3-Slot CSQ Plexi XSPC RX 240 
OSPowerCaseOther
Windows 7 Professional 64-Bit Corsair AX760 Corsair Obsidian 750D RGB LED Strips w/ Controller 
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