Re: Questions

[Adam Goryachev <mailinglists@websitemanagers.com.au>]

On 16/02/2016 22:46, o1bigtenor wrote:
> On Mon, Feb 15, 2016 at 4:05 PM, Adam Goryachev
> <mailinglists@websitemanagers.com.au> wrote:
>
>
>> I wanted to mention this, what drives do you have right now, and do know
>> about SCT ERC?
>> Maybe start here (but you probably need to read more):
>> http://www.spinics.net/lists/raid/msg48199.html
> A major reason as to why the drives are getting replaced. Back in early 2012
> when I setup the machine there was no obvious information that the ERC
> type drives were needed so I just bought vanilla drives.
>> Essentially, your current disks might be fine, but if you don't have the
>> right settings, they could be "failing" regularly putting your data at risk.
>> You should fix any issue here before you attempt to replace your drives.
> I now have 2 long term drives which are likely still good and 2 cheap
> drives that
> are quite new but which I don't trust for long term reliability,
> therefore the push
> to change them all.

Note, most drives either still support it, or else can be worked around 
to avoid the timeout mismatch. You should do this before continue to 
replace the drives, as you want to avoid this happening in the middle of 
replacing drives.
>>> the fail remove and add process 4 seperate times might not be a good thing
>>> but I do not know of a different option. Compounding the difficulty is
>>> that there
>>> are no empty hard drive slots in the machine. I do have an external USB
>>> 3.0
>>> 2 drive holder that could be used.
>>>
>>> The only suggestion in all the documents I perused was to place spare
>>> drives
>>> into something like this external box and then add the drives into the
>>> array.
>>> The process was not laid out and leaves me with a number of questions.
>>>
>>> Is there a suggested method for replacing ALL the drives in an array (raid
>>> 10
>>> in this case)?
>>
>> In order to replace all drives, I would suggest that you simply replace one
>> drive 4 times (different drive each time).
>> The first question to ask, is your external USB drive bay reliable? If not,
>> then there are other solutions that are probably less dangerous.
>>
>> So, add your spare drive to the external USB drive bay, it should show up as
>> /dev/sdy (for example)
>> Partition to match the rest of your existing drives
>> Add the new partition to your existing array: mdadm --manage /dev/md0 --add
>> /dev/sdx1
>> Replace one of the existing drives with the new one: mdadm /dev/md0
>> --replace /dev/sda1 --with /dev/sdx1
>> Personally, because I distrust the external USB drive bay (don't ask me why,
>> it just seems less reliable than internal sata), once the drive has finished
>> being replaced, I would shutdown, remove the old drive, and install the
>> replacement drive, then add another new spare, and repeat.
>>
>> You can see this page for some extra information:
>> http://unix.stackexchange.com/questions/74924/how-to-safely-replace-a-not-yet-failed-disk-in-a-linux-raid5-array
>>> If I use the external box how do I do this (external box only holds 2
>>> drives) so
>>> that I can transfer the information on the drives from the array to
>>> the new drives
>>> and then just replace the drives 2 at a time into the machine without
>>> there being
>>> issues because in the information transfer the drives will be sdg and
>>> sdh (AFAIK)
>>> and later they will be some of sdb, sdc, sde, and/or sdf.
>> I would suggest replacing one at a time.
> There is no way to do them one after another copying over all four and then
> only needing to shut the box down once or failing that doing the process 2 times
> necessitating only 2 shutdowns instead of 4 is there? The external USB box
> does have room for 2 drives at once.

Put two blank drives into the USB, replace first one, replace second one 
(would suggest second drive as non-matching pair). Shutdown, move two 
new drives internal, place two new drives into drive bay, and repeat for 
the last two drives.

I would suggest adding a bitmap for at least the time you are doing the 
replacements, then if you have a failure on the USB enclosure during the 
2nd or 4th drive, at least the 1st or 3rd will re-sync quickly.

Regards,
Adam