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Re: RAID 6 mdadm

Am Wednesday 10 April 2013 17:21:35 schrieb Muhammad Yousuf Khan:
> exactly, i am using RAID 1 with mdadm and not more then 230 or 300MB
> throughput.  and the people are harnessing 4GB so this is the point where i
> am confused

You cannot get more than about 200MB/s out of a RAID1 setup, not even with 
15krpm SAS drives. the RAID1 will never be faster than a single disk. How 
would it.

If you want to saturate 4G*bit* ethernet (gigaBIT! not byte!) which comes down 
to 500MB/s raw across all interfaces, so 125MB/s on one nic you definetly do 
*not* want linux softraid 6. either patch up the kernel with ZFS or if you 
wanna cross the t's and dot the i's: get a HP Proliant N40L, put a 
KVR1333D3E9SK2/16G 2x8GB ECC mem kit in it, install FreeNAS, add 4 7k2 rpm 
drives of your choice and create a z-raid over it, you should see 400MB/s.
Has 2 slots, on pcie16x, one 1x so should take a 4xGBE card and there you go.
Due to the massive caching and whatnot zraid uses and hence the amount of data 
in the 16GB make sure it's UPS backed. So far we're looking at roundabout 450 
USD without disks and UPS, but you'll have one heck of a NAS.

Now, *this* totally is not debian anymore, so back on topic:

I have a 5x1500GB raid5 from 72krpm sata drives and without optimizations, 
LVM2 and xfs on top of it get about 80MB/s write speed. raid6 probably would 
slow to a crawl (platform is a core i5 quad @2.3GHz)

> On Wed, Apr 10, 2013 at 7:38 PM, Gary Dale <garydale@rogers.com> wrote:
> > On 10/04/13 10:15 AM, Muhammad Yousuf Khan wrote:
> >> i was watch a person's video regarding RAID 6 with mdadm
> >> his configuration was very low, some old system probably
> >> 2GB RAM, 3x8TB Hard Drives, 4port Ethernet card for channeling.

There is no such thing as a 8TB hard drive in the year 2013....

> >> and the guy was giving review of his home server. he says he will
> >> channel the 4 port Ethernet to achive 4Gbps network throughput. and 2
> >> drive redundancy with RAID6.

...maybe 8x3TB rahter with 2 spares?

> >>
> >> my question is
> >> since i can not invest that huge money for testing so just asking from
> >> experience users. isn't it going to be a problem because of bottleneck
> >> and limited throughput of SATA 7200 rpm 3TB drives?
> >>
> >> actually what i need is 4GB LAN throughput with teaming (802.3ad) for
> >> data storage to backup VMs and same huge data manipulations will be
> >> done. so just confused if it going to work or not.

VM storage: make that N40L FreeNAS a N54L and use block dedup. Cost more, but 
worth it.

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