[Gluster-users] Design/HW for cost-efficient NL archive >= 0.5PB?

[bernhard glomm]

some years ago I had a similar tasks.
I did:
- We had disk arrays with 24 slots, with optional 4 JBODS (each 24 slots) stacked on top, dual LWL controller 4GB (costs ;-) 
- creating raids (6) with not more than 7 disks each
- as far as I remember I had one hot spare per each 4 raids
- connecting as many of this raid bricks together with striped glusterfs as needed
- as for replication, I was planing for an offside duplicate of this architecture and
because losing data was REALLY not an option, writing it all off at a second offside location onto LTFS tapes.
As the original version for the LTFS library edition was far to expensive for us 
I found an alternative solution that does the same thing
but fort a much reasonable prize. LTFS is still a big thing in digital Archiving.
Give me a note if you like more details on that.

- This way I could fsck all (not to big) raids in parallel (sped things up)
- proper robustness against disk failure
- space that could grow infinite in size (add more and bigger disks) and keep up with access speed (ad more server) at a pretty foreseeable prize
- LTFS in the vault provided just the finishing having data accessible even if two out three sides are down, 
reasonable prize, (for instance no heat problem at the tape location)
Nowadays I would go for the same approach except zfs raidz3 bricks (at least do a thorough test on it) 
instead of (small) hardware raid bricks. 
As for simplicity and robustness I wouldn't like to end up with several hundred glusterfs bricks, each on one individual disk,
but rather leaving disk failure prevention either to hardware raid or zfs and using gluster to connect this bricks into the
fs size I need(  - and for mirroring the whole thing to a second side if needed)
hth
Bernhard



	 Bernhard Glomm
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On Dec 25, 2013, at 8:47 PM, Fredrik Häll <hall.fredrik at gmail.com> wrote:

> I am new to Gluster, but so far it seems very attractive for my needs. I am trying to assess its suitability for a cost-efficient storage problem I am tackling. Hopefully someone can help me find how to best solve my problem. 
> 
> Capacity: 
> Start with around 0.5PB usable
> 
> Redundancy: 
> 2 replicas with non-RAID is not sufficient. Either 3 replicas with non-raid or some combination of 2 replicas and RAID?
> 
> File types: 
> Large files, around 400-1500MB each. 
> 
> Usage pattern: 
> Archive (not sure if this matches nearline or not..) with files being added at around 200-300GB/day (3-400 files/day). Very few reads, order of 10 file accesses per day. Concurrent reads highly unlikely. 
> 
> The main two factors for me are cost and redundancy. Losing data is not an option, being an archive solution. Cost/usable TB is the other key factor, as we see growth estimates of 100-500TB/year.
> 
> Looking just at $/TB, a RAID-based approach to me sounds more efficient. But RAID rebuild times with large arrays of large capacity drives sound really scary. Not sure if something smart can be done since we will still have a replica left during the rebuild?
> 
> So, any suggestions on what would be possible and cost-efficient solutions? 
> 
> - Any experience on dense servers, what is advisable? 24/36/50/60 slots?
> - SAS expanders/storage pods?
> - RAID vs non-RAID?
> - Number of replicas etc? 
> 
> Best, 
> 
> Fredrik
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