RAID 5 vs RAID 6 - performance?

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crushdepth
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RAID 5 vs RAID 6 - performance?

Post by crushdepth » Tue Jun 09, 2009 11:58 am

Does anyone know how RAID 5 and RAID 6 compare in terms of read/write speed? I would like to set up RAID 6 on my work's file server, but I am wondering if there is any performance penalty compared to RAID 5. Also, is the rebuild time slower under RAID 6, or is it similar?

I want to set up a file server and backup server for work this week (two TS-639 units). On paper I prefer RAID 6 because it has better redundancy, but I am wondering if there is much difference in performance?

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QNAPJason
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Re: RAID 5 vs RAID 6 - performance?

Post by QNAPJason » Tue Jun 09, 2009 12:19 pm

Dear customer,
The difference in speed between RAID5 & RADI6 on a TS-639 Pro is as follows.

Here's our lab test:
TS-639 Pro (MB/s)
SAMBA Write SAMBA Read FTP Write FTP Read
RAID5 63.7 88 76.1 55.7

RAID6 67.3 85.3 82 57.3

Hope this helps.

Sincerely

Jason

shake-the-disease
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Re: RAID 5 vs RAID 6 - performance?

Post by shake-the-disease » Tue Jun 09, 2009 12:28 pm

Writes will be slower on Raid-6 compared to Raid-5 due to the extra parity. How much slower I'm not sure. I would think reads would be the same as the parity calculation is only done on writes, not reads.
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Cybix
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Re: RAID 5 vs RAID 6 - performance?

Post by Cybix » Tue Jun 09, 2009 2:01 pm

under what conditions are the lab tests?

I can't get any more than 40MB/s using samba to read or write to my TS-639 with RAID5. using Cat5 cable and a Netgear GS608 gigabit switch. MTU1500

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Re: RAID 5 vs RAID 6 - performance?

Post by QNAPJason » Tue Jun 09, 2009 2:38 pm

Update:
Sorry that I should have been more clear.
Here's the testing environment:

software: IOzone 3.263

Test Server Performance-Test Server
Processor(s) Intel Core2 Quad CPU Q8200 2.34GHz
Memory 2GB
Main board ACER MCP73PV
HDD WD6400AAKS 620GB
Network Adapter(s) Intel PRO 1000 PT 82572
O.S. Windows Vista 32Bit SP1

PC-NAS direct connection

New RAID build.
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crushdepth
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Re: RAID 5 vs RAID 6 - performance?

Post by crushdepth » Tue Jun 09, 2009 2:50 pm

Ok thanks, much appreciated. So a RAID 6 is faster or at least similar - good news.

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Moogle Stiltzkin
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Re: RAID 5 vs RAID 6 - performance?

Post by Moogle Stiltzkin » Tue Jun 16, 2009 1:06 pm

Normally Raid 6 would be slower then Raid 5, but judging from the test it's more or less the same which is indeed good news :mrgreen:

But keep in mind you still suffer the hard drive space penalty. For example with 5 x 1 tb drives, you lose 20% of usable hard drive space. In addition to some space when you format the drives.

If you use Raid 6, you lose 40% of usable drive space !! Also in addition to some space when you format the drives. The only benefit i would think Raid 6 then have over Raid 5, is the following:

1. in raid 5 if 1 drive fails, your raid won't fail but you will need to replace the failed drive with a new working one and then rebuild. If another drive fails again during this period, your data is all gone. By the way when just only 1 drive fails, you are under degraded performance because of it.

2. Raid 6 solves this by allowing 2 drives to fail. Only if a third one fails would you lose all your data. The problem is, if you lose 1 drive, you also still revert back to the degraded performance until your rebuild is completed.
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