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 ri...@alldigital.com -
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- To err is human. To forgive, a large sum of money is needed. -
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