Assistance building a backup server

[Rick Stevens]

On 03/05/2015 08:48 AM, Alex Regan wrote:
> Hi,
> I have a fedora20 system acting as a backup server, and I've exceeded
> its capacity. I'd like to build a bigger one, probably using fedora21.
>
> I currently have a 3TB backup system using five 1TB disks in RAID5.
> Restore times in case of disk failure are already exceedingly long, so
> I'd like to consider another method of providing redundancy, and would
> like suggestions.

Five 1TB disks in a RAID5 should give you about 4TB usable storage. Are
you sure you're not using RAID6 (two parity drives)?

> I'd like to have 6TB of usable space using 2TB disks.

Four 2TB drives in a RAID5 or five 2TB drives in a RAID6 would give you
this. I'd vote for the RAID6.

> Is ext4 still best for this?

BTRFS or (gulp!) XFS might be better, although ext4 would work.

> Some RAID variant or is there something better?

The bigger the partition (LUN, PV, LV, whatever), the longer the
recovery times are in case of a disk failure. I run a number of very
large storage platforms (>500TB) and as soon as any LUN hits the 1TB
mark, I immediately go to RAID6, simply because there is a possibility
that a second drive may go bad while the first one is rebuilding. RAID6
gives me that cushion.

There are a couple of things I do:

1. I prefer using hardware RAID over software RAID. More expensive, but
I feel it's more reliable.

2. I like using hot-swappable drive arrays so drive replacement is easy.

3. I like having my drives from different manufacturing batches because
(and this is just based on experience--I can't prove it) when one drive
from a batch dies, another from that same batch with the same number of
running hours on it will likely die soon.

> Are there any NAS projects that may be beneficial?

The underlying technology of the drive arrays will be the same in a
NAS as a SAN. It's only the access method that's different and the fact
that some attributes (permissions, ACLs, etc.) may not be translatable
between the native system and a NAS. Generally they are translatable on
a SAN (and I include raw SAN LUNs shared via iSCSI in this) simply
because it is a directly coupled system and uses the host's native
filesystems.

Your mileage may vary and I'm sure others on the list have equally
strong opinions.
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- Rick Stevens, Systems Engineer, AllDigital    ricks at alldigital.com -
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