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Another SAS vs SATA Question

Marzipan

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I have a client that is looking at a SAN with 24 bays fully populated with 12 - 18TB HDD. They intend to have it setup as a RAID 6 array.

I know SAS is the better option, but currently we can only get up to 14TB HDD for SAS while we can get 18TB in SATA3.

From what I've been told, the SAN will primarily be an archive for hundreds of thousands of images which will be connected to a DL380 G10 Plus server and through that, they said only 5 to 10 people / devices max will be connecting.

with that use case, would going with the larger SATA3 drives impair the NAS in any significant way?

also, a question about their intended RAID configuration. RAID 6 is different from 5 in that it can lose up to 2 HDD before the array collapses. How many hot spares can you ideally have on RAID 6? Two makes the most sense, but I wonder if there is any logic to a third or fourth hot spare simply based on the theory that two drives could die in a short time but recover fast enough hat they aren't replaced so the third / fourth can be a safety net.

I know there are lots of other ways to create massive storage arrays, but this is a government client and all the other ways aren't an option because nobody has the training to deploy them, so it's a total unknown and the risk level of doing so is unacceptably high if / when there are issues.

Assuming the customer decides to go with the 14TB SAS, what RAID configuration would you recommend for 24 of them, for best redundancy?
 

Cptn Vortex

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Which SAN? Price wise, they are way better off going with one of the enterprise QNAPs with ZFS. It will more likely be FAR cheaper overall, and probably better performance especially with accessing images. RAID is old, no one is really using it any more. Do a ZFS with 2 or more drive redundancy, 1GB RAM per TB, and if they need the fastest of the fast, they could do a SSD cache using enterprise SSDs : https://www.qnap.com/solution/qnap-zfs/en/

And there are Exos SAS drives that are reasonably priced IIRC
 

lcdguy

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For any raid configuration you should have at a minimum 1 hot spare per drive type regardless of raid level. RAID-6 uses 2 disks for parity so yes you can loose up to 2 drives in a RAID-6 configuration before suffering data loss, but i would never want to run a raid configuration without hotspares, that's just asking for trouble :)

Also you seem to be talking about 2 different things a SAN is not a NAS (SAN is the storage network connecting your hosts to your storage array) as they use different protocols for accessing data (ie: Block Protocols vs File Protocols). Depending on how they will be accessing the storage should also be taken into account as that should help narrow down the solutions.

In regards to SATA vs SAS vs Flash that will really depend on what kind of performance requirements there are for the solution, such as how many iops does the workload need ?

For example if it's just a place to dump a bunch of files that don't need high level of performance than going with SATA drives might be the best solution.
 

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