Re: [gentoo-user] backup hardware setup

[Alan McKinnon]

On 24/06/2014 20:34, meino.cramer@×××.de wrote:
> Alan McKinnon <alan.mckinnon@×××××.com> [14-06-24 20:00]:
>> On 24/06/2014 19:32, meino.cramer@×××.de wrote:
>>> Alan McKinnon <alan.mckinnon@×××××.com> [14-06-24 19:12]:
>>>> On 24/06/2014 16:43, meino.cramer@×××.de wrote:
>>>>> Hi,
>>>>>
>>>>> I bought two identical external harddrives, USB 3.0, with 1 TByte each
>>>>> (no SSD - the good ole mechanical ones...;).
>>>>>
>>>>> The intended use is for backup of longer files. The drives will
>>>>> contain the same contents.
>>>>>
>>>>> Currently there are still "clean metal" (no partitioning, no fs).
>>>>>
>>>>> Data integrity and recoverability (Uhhh...that words looks wrong...) in
>>>>> case of an desaster is more important than speed.
>>>>>
>>>>> What is the recommended way of partitioning ?
>>>>> What filesystem to choose?
>>>>>
>>>>>
>>>>> Thank you very much in advance for any help!
>>>>> Best regards,
>>>>> mcc
>>>>>
>>>>>
>>>>> PS: Running vanilla kernel 3.15.1....
>>>>
>>>> You haven't given much in the way of detail, so I assume you have
>>>> regular needs, nothing fancy, and it's all a bunch of files right?
>>>>
>>>> In that case, partitioning and filesystem type are largely irrelevant as
>>>> long as you don't have corruption. With one caveat:
>>>>
>>>> You must always make sure the source drive is intact and ok. If not, and
>>>> you back it up anyway, then you are already toast (you will overwrite
>>>> your last backup with new faulty data).
>>>>
>>>> There's several approaches to how to do the transfer:
>>>>
>>>> If you have say a general fileserver with lots of files that don't
>>>> change much or often, just rsync everything in one go. There is no
>>>> optimization you can do that will perform much faster than rsync.
>>>>
>>>> If you have a big busy filesystem that changes often and lots, then use
>>>> lvm (or anything that can make snapshots) and rsync that.
>>>>
>>>> If you have a huge database where everything is changing all the time,
>>>> don't do filesystem copies, use the tools provided by the db vendor. I
>>>> doubt this is your need as you would have said so, but it's worth
>>>> mentioning.
>>>>
>>>>
>>>> --
>>>> Alan McKinnon
>>>> alan.mckinnon@×××××.com
>>>>
>>>>
>>>
>>> Hi Alan,
>>>
>>> thanks for your reply! :)
>>>
>>> Yes...your are right. I have a lot static (=not changing) data on my
>>> harddisk...mostly things like video tutorials (blender), videos of
>>> birds I filmed, dokuments and such...
>>>
>>> They are eating up the space on my systems harddisk.
>>>
>>> Do I decided to put them on a extern hd and an identical copy on
>>> another identical external harddisk.
>>>
>>> Its mainly a task of updateing the data on the external drives with
>>> that what is new (and static and big and falls under what I described
>>> above) on my systems harddisk.
>>>
>>> I will check rsync for that!
>>
>>
>> That changes things just a little bit - I thought your two drives were
>> going to be one for live and one for backup. Do you intend to move these
>> files off your main drive onto the identical externals, or just copy the
>> files?
>>
>> I would have those two external drives using different filesystems, just
>> in case as they are your only copy and external drives are fragile in
>> use and in storage. Exact fs type doesn't really matter - ext4 and xfs,
>> or ext* and btrfs, it's all good.
>>
>> Just do make sure you don't use rsync with --delete for this :-)
>>
>>
>>
>> --
>> Alan McKinnon
>> alan.mckinnon@×××××.com
>>
>>
>
> Yes, I will delete the data from my systems drive...
>
> You wrote:
> "I would have those two external drives using different filesystems"
>
> Different to what? Different to the fs on the system drive? Both
> external drives use different filesystems? All three use different
> filesystems?


Different to each other


> And how can this help, if the drives are fragile? (I understand
> "fragile" as "mechanical not robust" (sorry I am no native english
> speaker))

If one drive is say btrfs and the other say ext4 and you hit a
corruption bug in btrfs, then you still have an uncorrupted ext4 copy

>
> I will use this "mobile disks" not really as the word "mobile" implies. They
> will only "travel" manually between a secure place and my PC.
> When in use, they will rest on the floor of the room (so they can not
> be dropped) and _under_ the case of my PC (ole school big tower metal
> case with a gap between the bottom of the case and the floor of the
> room.)


External drives have a much higher failure rate than internal drives.
people don't expect them to fail or be dropped or accidentally plugged
in in the wrong order and the wrong one to be mkfs'ed (until it does
happen). These are real risks that you can't ignore whereas with a good
internal drive you can often get away with it.

So it only make sense to take sensible precautions that cost you very
little, especially considering these two drives will be your only copy.



-- 
Alan McKinnon
alan.mckinnon@×××××.com