Resync raid array problem

Resync raid array problem

[Tarak]

Hi 
We sucessfully created a Raid array of 8 harddisks.
On power failure situation, the resync of raid array 
is taking too much of time almost equal to 
the time taken for creating the raid array of hard disks.
Anyone is having an idea about this..
Please help me on this.

Regards
Tarak

Re: Resync raid array problem

[Keith Keller]

On 2013-05-20, Tarak <tarakramgopal@gmail.com> wrote:
> We sucessfully created a Raid array of 8 harddisks.
> On power failure situation,

You should probably have some sort of redundant power for such an
array--either a UPS or backup power provided by a building generator.

> the resync of raid array 
> is taking too much of time almost equal to 
> the time taken for creating the raid array of hard disks.

IIRC, a RAID5 is created by making the array in degraded mode and
resyncing the array.  So "create" and "resync" are basically equal in
duration in this scenario.  (I think creating a RAID6 works differently,
but it's possible that create and resync times are comparable as well.)

--keith


-- 
kkeller@wombat.san-francisco.ca.us

Re: Resync raid array problem

[Brad Campbell]

On 20/05/13 10:53, Keith Keller wrote:
> On 2013-05-20, Tarak <tarakramgopal@gmail.com> wrote:
>> We sucessfully created a Raid array of 8 harddisks.
>> On power failure situation,
>
> You should probably have some sort of redundant power for such an
> array--either a UPS or backup power provided by a building generator.
>

Can't agree with this strongly enough. Grab the best UPS you can afford 
(and often that means getting a 10 year old one second hand and 
replacing the batteries). Best investment I _ever_ made was a 2000 
vintage APC SmartUPS 2200 and it cost all of about $200 second hand, 
plus another $100 for new batteries.

Also, look at adding a bitmap to your array. Then it will only resync 
what it suspects might be dirty.

Re: Resync raid array problem

[Roy Sigurd Karlsbakk]

> On 20/05/13 10:53, Keith Keller wrote:
> > On 2013-05-20, Tarak <tarakramgopal@gmail.com> wrote:
> >> We sucessfully created a Raid array of 8 harddisks.
> >> On power failure situation,
> >
> > You should probably have some sort of redundant power for such an
> > array--either a UPS or backup power provided by a building
> > generator.
> >
> 
> Can't agree with this strongly enough. Grab the best UPS you can
> afford
> (and often that means getting a 10 year old one second hand and
> replacing the batteries). Best investment I _ever_ made was a 2000
> vintage APC SmartUPS 2200 and it cost all of about $200 second hand,
> plus another $100 for new batteries.
> 
> Also, look at adding a bitmap to your array. Then it will only resync
> what it suspects might be dirty.

oh - and if this is a raid-5 array, better get a new disk and change to raid-6. 8 drives in raid-5 is rather a lot…

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: Resync raid array problem

[Sam Bingner]

On May 19, 2013, at 3:57 PM, Tarak <tarakramgopal@gmail.com> wrote:

> Hi 
> We sucessfully created a Raid array of 8 harddisks.
> On power failure situation, the resync of raid array 
> is taking too much of time almost equal to 
> the time taken for creating the raid array of hard disks.
> Anyone is having an idea about this..
> Please help me on this.
> 
> Regards
> Tarak

If you enable a bitmap on the device it should significantly lower the resync times.... but of curse this should not be a normal occurrence, or you have bigger problems...

Sam