Hot replacing device in RAID 6

Hot replacing device in RAID 6

[Patrik Horník]

Hello Neil,

I want to ask for best solution for replacing device in RAID 6 array.
I want to replace device (actually RAID 0 array of two drives), which
is working OK but there is known problem with firmware of one drive of
that RAID 0 and no solution for it. (It can cause lock up of the
drive, which happened to me.)

I want to minimize risk of problems on any device / devices during
adding new drive, so I am considering other solutions than remove old
and add new.

- We discussed couple of years ago hot replacing the drive. I see it
is now supported in mdadm. Is it rock stable and can be used on
production data? I have kernel and mdadm from debian testing, 3.14-2
and 3.3-2. Were there some important fixes from these versions? I have
this server on UPS but not on aggregator so there is real danger of
power outage and need to shutdown the array during operation.

- I can take the array offline. Is it good solution to simply copy the
old device to new device?

- Or do you suggest as safest solution to remove old device and add new one?

Thanks.

Best regards,

Patrik

Re: Hot replacing device in RAID 6

[Mikael Abrahamsson]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1030 bytes --]

On Sun, 5 Oct 2014, Patrik Horník wrote:

> I want to ask for best solution for replacing device in RAID 6 array.
>
> - We discussed couple of years ago hot replacing the drive. I see it
> is now supported in mdadm. Is it rock stable and can be used on
> production data? I have kernel and mdadm from debian testing, 3.14-2
> and 3.3-2. Were there some important fixes from these versions? I have
> this server on UPS but not on aggregator so there is real danger of
> power outage and need to shutdown the array during operation.

I have successfully used the replace function without ill effects, and I 
believe this was with a 3.8.x kernel. The function itself has been around 
since 3.3 or so.

I don't want to give you any recommendations, but next time I need to 
replace a failing drive that is still operational enough to stay in the 
raid, personally I will use the replace function. The code is a few years 
old by now and I imagine it has been used quite a lot by now.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: Hot replacing device in RAID 6

[Keith Keller]

On 2014-10-05, Patrik Horník <patrik@dsl.sk> wrote:
>
> - We discussed couple of years ago hot replacing the drive. I see it
> is now supported in mdadm. Is it rock stable and can be used on
> production data?

I have used replace a handful of times with great success and no
problems.  I have not had to shut down the array during the rebuild
operation, however.  I suspect (but have no direct evidence) that a
clean shutdown should be fine.  I used kernel 3.9 from ELRepo for
the replace.

--keith


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


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Re: Hot replacing device in RAID 6

[Patrik Horník]

Thanks for assistance, it seems that everything worked fine. But I
need yet to check the array to be sure.

2014-10-05 20:30 GMT+02:00 Keith Keller <kkeller@wombat.san-francisco.ca.us>:
> On 2014-10-05, Patrik Horník <patrik@dsl.sk> wrote:
>>
>> - We discussed couple of years ago hot replacing the drive. I see it
>> is now supported in mdadm. Is it rock stable and can be used on
>> production data?
>
> I have used replace a handful of times with great success and no
> problems.  I have not had to shut down the array during the rebuild
> operation, however.  I suspect (but have no direct evidence) that a
> clean shutdown should be fine.  I used kernel 3.9 from ELRepo for
> the replace.
>
> --keith
>
>
> --
> kkeller@wombat.san-francisco.ca.us
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
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