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Author Topic: Raid 0 performance  (Read 3396 times)

Dalsvzla

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  • Posts: 31
Raid 0 performance
« on: September 15, 2012, 07:01:14 AM »

Hi,

Im reading in other post that you may not notice any gain in speed with RAid 0 option because the choke element in these NAS's is almost always the CPU... so do do yo recomend conigure the NAS in JBOD instead Raid 0?

regards
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ivan

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Re: Raid 0 performance
« Reply #1 on: September 15, 2012, 03:04:57 PM »

It all depends on what you want to do with your DNS-320.

The manual has a very good section describing the various options for setting up the disks.  You need to read that and then decide what you want and implement it.

Whatever you decide on make sure you also have a good backup strategy and test that it works!
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Dalsvzla

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  • Posts: 31
Re: Raid 0 performance
« Reply #2 on: September 15, 2012, 07:30:04 PM »

It all depends on what you want to do with your DNS-320.

The manual has a very good section describing the various options for setting up the disks.  You need to read that and then decide what you want and implement it.

Whatever you decide on make sure you also have a good backup strategy and test that it works!

Hi Ivan,

I want a make the decision just in terms of read speeds.

Look this:

NAS performance tester 1.4 http://www.808.dk/?nastester
Running warmup...
Running a 400MB file write on drive z: 5 times...
Iteration 1:     18.08 MB/sec
Iteration 2:     18.46 MB/sec
Iteration 3:     19.84 MB/sec
Iteration 4:     18.35 MB/sec
Iteration 5:     17.41 MB/sec
------------------------------
Average (W):     18.43 MB/sec
------------------------------
Running a 400MB file read on drive z: 5 times...
Iteration 1:     8.39 MB/sec
Iteration 2:     8.45 MB/sec
Iteration 3:     8.82 MB/sec
Iteration 4:     8.60 MB/sec
Iteration 5:     9.07 MB/sec
------------------------------
Average (R):     8.67 MB/sec
------------------------------
Running warmup...
Running a 400MB file write on drive x: 5 times...
Iteration 1:     22.13 MB/sec
Iteration 2:     21.13 MB/sec
Iteration 3:     22.12 MB/sec
Iteration 4:     21.61 MB/sec
Iteration 5:     22.24 MB/sec
------------------------------
Average (W):     21.85 MB/sec
------------------------------
Running a 400MB file read on drive x: 5 times...
Iteration 1:     53.14 MB/sec
Iteration 2:     48.64 MB/sec
Iteration 3:     57.77 MB/sec
Iteration 4:     47.02 MB/sec
Iteration 5:     49.62 MB/sec
------------------------------
Average (R):     51.24 MB/sec
------------------------------

The first one is a DNS-320 Raid 0 with two 2TB disk and the second one is a DNS-320 JBOD with 3TB & 1TB disk (firstone backup)

Im seeing that JBOD are to much effectively in speed terms...whys that? In this case im thinking to convert both DNS-320 in JBOD.

The firstone is a multimedia stream server and also documents backups, second one is backup nas (first one)

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ivan

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Re: Raid 0 performance
« Reply #3 on: September 16, 2012, 07:56:19 AM »

Any RAID setup will be slower than just writing/ reading disks because of the housekeeping necessary. 

If you look at the diagrams provided in the manual you should see what I am referring to. 

The moment anything is split and spread across disks the information has to be stored on the disks to allow it to be retrieved so slowing both the write and read speeds.

This overhead is somewhat reduced in servers and industrial NAS products by the use of 10,000rpm disks - not something generally found in a home NAS.
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Dalsvzla

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  • Posts: 31
Re: Raid 0 performance
« Reply #4 on: September 17, 2012, 03:24:05 PM »

Any RAID setup will be slower than just writing/ reading disks because of the housekeeping necessary. 

If you look at the diagrams provided in the manual you should see what I am referring to. 

The moment anything is split and spread across disks the information has to be stored on the disks to allow it to be retrieved so slowing both the write and read speeds.

This overhead is somewhat reduced in servers and industrial NAS products by the use of 10,000rpm disks - not something generally found in a home NAS.


Im not seeing nothing else on diagrams but the Raid theory. DNS-320 does work with Raid 0 so had to do the job, however, you are telling me in less words that the DNS-320 does not work any well with Raid 0 because of hardware... ill change to JBOD and let you know.


Thks.
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RicRoller

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  • Posts: 45
Re: Raid 0 performance
« Reply #5 on: September 18, 2012, 12:06:47 AM »

RAID 0 should be faster than a single disk for sequential access to large files, because only half as much data is stored on each disk. But it won't be anywhere near twice as fast due to the overheads in managing the RAID set.

But for smaller files, of a similar or smaller size than the "stripe size" of the RAID 0 array there is no speed benefit, and as Ivan pointed out, performance could actually be worse.

Note that with JBOD (as with RAID 0); a failure of one disk and you could lose the entire contents of both disks (e.g. if the failed disk contained the partition table and/or directory information pertaining to files physically residing on the other disk). My personal preference would be to have two independent volumes ("standard") if I needed to maximise the total storage space, or RAID 1 if I needed to maximise the reliability.

Regards,
Richard
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