[Techtalk] xfs repartitioning

[Ricardo Dalceno]

Hi Maryll,


AFAIK there is no such disk with 80TB yet, so, i suppose you are using some
kind of  RAID 0 to get that numbers, right ?

If you are going to use this in production (data cannot be lost) you should
have another raid with 80TB too, and make a RAID 10 (at least).
Then, IMHO, use gparted and create a logical volume group. Inside this VG,
create 4 (or more) logical volumes and format them as XFS (or any other
filesystem you want to use).

In my experience, XFS is great when you have to deal with large files and
have large blocks written/read at a time. If you have large files, but the
blocks writen are small (4k at a time) it will not perform well.

Good luck and may the force be with you...


-----
Ricardo 'j0k3r' Dalceno

2015-10-17 6:38 GMT-03:00 James Sutherland <j at sutherland.pw>:

> On 17/10/2015 02:44, Meryll Larkin wrote:
>
>> Requesting guidance from someone with experience in LARGE partitions & xfs
>> file systems.
>>
>
> They are two separate issues, remember: you partition the disk, then you
> put some file system on it afterwards. XFS isn't involved in partitioning.
>
> I would like to reformat the 80T partition into 4 20T partitions - I need
>> guidance with this.  Anyone?
>>
> ...
>
>> I am NOT a novice at all, but I am new at such large drives and xfs.  For
>> example, I thought that I could use familiar fdisk (wrong).
>>
>
> Yes. Remember, the original partitioning system (known as MBR) was
> designed when disks were sized in megabytes; anything over, IIRC, 2T it
> just can't cope with, all the clever tricks people came up with to stretch
> capacity finally ran out, and since fdisk only understands MBR partitions,
> the disk is far too big for fdisk to cope.
>
> For that size, you need the new style ("GPT") partition table instead.
> There's a GPT version of fdisk, called gdisk, or you can use one of the
> multi-purpose tools instead, like gparted as A Mani suggested in her reply.
>
> 1.  Least favorite but most likely to work:  run CentOS 6 installer again
>> and reformat that one partition.  I have a vague idea about doing this,
>> but
>> if someone has done it, pointers would be appreciated.
>>
>
> The installer will just run something like gparted for you - easier to run
> it directly and avoid reinstalling.
>
> 2.  Use mkfs.xfs  but I am unsure about the syntax and don't know if I need
>> to first do something else like write zeros to the 80 T partition.  Or
>> will
>> the -f (force) switch work?
>>
>
> No, bad idea. mkfs.xfs is for formatting partitions, not for creating them.
>
> Apart from the fact you need the newer partition table format, you can
> treat this exactly as if you had an 80 G disk to be split into 4: delete
> the one big partition, create then format the four new ones, job done.
> Because of the size, you need the new GPT tools though: gdisk not fdisk, or
> GPartEd in GPT mode not MBR.
>
>
> James.
>
>
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-- 
Ricardo D. Dalceno
"All the world is a stage"