RAID-10 with mixed block size HDDs

RAID-10 with mixed block size HDDs

[Piergiorgio Sartor]

Hi all,

I've a two disk RAID-10 (far 2, I guess).
One HDD seems to be going to the HDD heaven,
so I'm planning to change it.

The most convenient HDD I found has 4K sectors,
while the actual ones have 512 byte sectors.

All partitions and headers seem to be multiple
of 4K, but I was wondering if there could be
performance problems having a mixed setup.

Any experience with that?
Suggestions?

Thanks,

bye,

-- 

piergiorgio

Re: RAID-10 with mixed block size HDDs

[Chris Murphy]

On Mar 25, 2013, at 12:04 PM, Piergiorgio Sartor <piergiorgio.sartor@nexgo.de> wrote:

> Hi all,
> 
> I've a two disk RAID-10 (far 2, I guess).
> One HDD seems to be going to the HDD heaven,
> so I'm planning to change it.
> 
> The most convenient HDD I found has 4K sectors,
> while the actual ones have 512 byte sectors.

It is a 4Kn drive, or a 512e drive? If it's 512e, as long as you add the whole disk or ensure alignment, it's OK. For 4Kn drives, that may be a problem. But so far I've only seen 4Kn drives as large 3+TB external USB.


Chris Murphy

Re: RAID-10 with mixed block size HDDs

[Piergiorgio Sartor]

On Mon, Mar 25, 2013 at 05:09:00PM -0600, Chris Murphy wrote:
> 
> On Mar 25, 2013, at 12:04 PM, Piergiorgio Sartor <piergiorgio.sartor@nexgo.de> wrote:
> 
> > Hi all,
> > 
> > I've a two disk RAID-10 (far 2, I guess).
> > One HDD seems to be going to the HDD heaven,
> > so I'm planning to change it.
> > 
> > The most convenient HDD I found has 4K sectors,
> > while the actual ones have 512 byte sectors.
> 
> It is a 4Kn drive, or a 512e drive? If it's 512e, as long as you add the whole disk or ensure alignment, it's OK. For 4Kn drives, that may be a problem. But so far I've only seen 4Kn drives as large 3+TB external USB.

Hi Chris,

thanks for the answer.

Reading the specs it seems it can emulate the 512,
so it should be a 512e.

Thanks again,

bye,

pg

> 
> 
> Chris Murphy

-- 

piergiorgio

Re: RAID-10 with mixed block size HDDs

[Roy Sigurd Karlsbakk]

----- Opprinnelig melding -----
> Hi all,
> 
> I've a two disk RAID-10 (far 2, I guess).

You can't grow a RAID-10…

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 98013356
roy@karlsbakk.net
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
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Re: RAID-10 with mixed block size HDDs

[Piergiorgio Sartor]

On Fri, Mar 29, 2013 at 01:31:28AM +0100, Roy Sigurd Karlsbakk wrote:
> ----- Opprinnelig melding -----
> > Hi all,
> > 
> > I've a two disk RAID-10 (far 2, I guess).
> 
> You can't grow a RAID-10…

I know, I've to replace a disk, non add.

bye,

pg
 
> Vennlige hilsener / Best regards
> 
> roy
> --
> Roy Sigurd Karlsbakk
> (+47) 98013356
> roy@karlsbakk.net
> http://blogg.karlsbakk.net/
> GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
> --
> I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
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-- 

piergiorgio
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Re: RAID-10 with mixed block size HDDs

[Roy Sigurd Karlsbakk]

> > > Hi all,
> > >
> > > I've a two disk RAID-10 (far 2, I guess).
> >
> > You can't grow a RAID-10…
> 
> I know, I've to replace a disk, non add.

I just don't understand why anyone would create a two-drive RAID-10, losing the flexibility of a mirror, and gaining nothing (since it's only on two drives)

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 98013356
roy@karlsbakk.net
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
--
I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
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Re: RAID-10 with mixed block size HDDs

[David Brown]

On 29/03/13 14:15, Roy Sigurd Karlsbakk wrote:
>>>> Hi all,
>>>>
>>>> I've a two disk RAID-10 (far 2, I guess).
>>>
>>> You can't grow a RAID-10…
>>
>> I know, I've to replace a disk, non add.
>
> I just don't understand why anyone would create a two-drive RAID-10,
> losing the flexibility of a mirror, and gaining nothing (since it's
> only on two drives)
>

With "far" layout, linux RAID-10 on two harddisks will give you the 
safety of RAID-1 mirroring with /faster/ than RAID-0 speeds on reads. 
(Writes are often a little slower than standard RAID-1 due to more head 
movement, but slow writes can be buffered, while fast reads mean a 
faster machine.)

Yes, you lose a bit of flexibility, and it would be very nice if RAID-10 
could be re-shaped, grown, etc.  But for a desktop system in particular, 
RAID-10,far2 is the best you can get for two disks.


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