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e_merlin

Raid setup for home use - what do you recommend?

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ShadowPeo

Hmm... Thinking more about it, RAID 10 should still be better for 4 drives. A single drive failure in RAID 0+1 would mean both drives in that stripe go down and you're left with 2 drives still working with zero redundancy. A single drive failure in RAID 10 would mean 3 drives are still working and 2 of those drives will be mirrored still.

 

Again True, I cannot refute that argument

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awraynor

They never responded to my offer of $99 per drive vs. listed $109. 

 

As far as RAID I would like to have roughly 10TB available before redundancy to leave a cushion. 

 

RAID 10 would cut it pretty tight. Maybe use RAID5 or save my pennies for bigger drives. 

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Joe_Miner

I get uncomfortable with rebuild times with larger capacity drives and prefer RAID10

 

WD RE 4TB drives are running just under $200 at NE

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itGeeks

I get uncomfortable with rebuild times with larger capacity drives and prefer RAID10

 

WD RE 4TB drives are running just under $200 at NE

I hear what your saying & I hold my breath anytime I have to rebuild but I have a very good backup plan in place so its not the end of the world if I loose the array. On top of a good backup plan both onsite & offsite I run 2 Synology DS-1815+ in a (HA) Cluster so if one box goes down for any reason it automatically switches over to the other DS-1815+ in the cluster so I have plenty of time to fix things. Anyway lets not forget a RAID 10 maybe better allowing for two drives to fail, Those two drives can't be in the same group or your no better off then RAID 5. For those that don't know when using RAID 10 you will have two groups of drives, Think of it as two RAID 1's combining those two RAID 1 groups into a RAID 10 so if you have two drives fail in group A your SOL. RAID of any kind is a risk when rebuilding because of the stress it puts on the drives. RAID is no substitute for a well thought out backup plan because one day for one reason or another your going to need to restore from backups.

 

All the information provided in this thread has been really great info but that said the stats for what types of RAID types should or should not be used does not work for everyone as is the case with small NAS boxes. When using a 4 bay NAS most home users are going to need/want to cram as much storage into it as possible depending on cost & need so there is no headroom for RAID types such as RAID 10 or RAID 6 because you loose half the storage and in only a 4 bay NAS that's huge so in this case I believe a RAID 5 gives you the best balance for the buck. Just make sure you have a good backup plan. I run all my small NAS boxes with RAID 5 with drive sizes ranging from 4-6TB and I have never once had a meltdown during a RAD rebuild now that's not to say it would never happen but just that I never had it happen on any of my Synology NAS boxes.

 

Summing it all up, I believe mileage may vary with all this but for small 4, 5, Bay NAS boxes RAID 5 is the way to go, It will give you the most usable storage with some level of protection. When you get into the larger NAS's 8 Bay and above then I would say RAID 6 or 10. This is how I setup things whether the critics agree or disagree its worked well for me :)  

 

Here is a nice RAID calculator by Synology for anyone wanting to play with RAID types to see how much storage you get with each-

https://www.synology.com/en-us/support/RAID_calculator

 

This is a nice document by Synology on different RAID types https://help.synology.com/dsm/?section=DSM&version=5.2&link=StorageManager%2Fvolume_diskgroup_what_is_raid.html

Edited by itGeeks

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GotNoTime

I have a very good backup plan in place so its not the end of the world if I loose the array. On top of a good backup plan both onsite & offsite I run 2 Synology DS-1815+ in a (HA) Cluster so if one box goes down for any reason it automatically switches over to the other DS-1815+ in the cluster so I have plenty of time to fix things. Anyway lets not forget a RAID 10 maybe better allowing for two drives to fail, Those two drives can't be in the same group or your no better off then RAID 5. For those that don't know when using RAID 10 you will have two groups of drives, Think of it as two RAID 1's combining those two RAID 1 groups into a RAID 10 so if you have two drives fail in group A your SOL. RAID of any kind is a risk when rebuilding because of the stress it puts on the drives. RAID is no substitute for a well thought out backup plan because one day for one reason or another your going to need to restore from backups.

Yup. This is pretty much it. RAID with redundancy is just there to save you the time + effort of restoring your data from a backup. It isn't a substitute for regularly backing up your data to something offline. You should keep to a proper backup regime as well and keep some copies going back in time. RAID won't protect you against malware quietly corrupting data or accidentally deleting a file. A good well thought out backup system will.

 

For small NAS units, I agree with itGeeks that RAID5 is generally what people will use. Maximum capacity whilst having some redundancy is what will be picked in the vast majority of cases. For a 4 drive NAS, the safest solution in terms of redundancy is actually RAID6 since any 2 drives can fail and you're still protected. You take a severe performance penalty for using it though with the additional parity calculations and the very small number of spindles in your system. You also have to balance it with the risk during intensive rebuild process as several people have mentioned.

 

For actual servers, I use RAID6 with a hot spare and have a daily incremental backup with a weekly full backup. The array controller has a large NV cache and there is a tiered SSD cache running on top as well. I recently setup a small 10 drive server with 2.5" 15K RPM SAS drives and 1TB of NVMe SSDs. I get 900MB/s throughput for something that isn't in the SSD cache. Once data is in the SSD cache however, read requests are 1.5GB/s together with the latency and seek time benefits. It is running ESXi and it is all done by the RAID controller and ESXi itself which means it completely transparent to the VMs themselves.

 

In the long term, other technology such as ZFS will start to become more prominent as there are several benefits over RAID such as fixing the RAID5 write hole and continual self scanning with the ability to self heal.

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schoondoggy

Yup. This is pretty much it. RAID with redundancy is just there to save you the time + effort of restoring your data from a backup. It isn't a substitute for regularly backing up your data to something offline. You should keep to a proper backup regime as well and keep some copies going back in time. RAID won't protect you against malware quietly corrupting data or accidentally deleting a file. A good well thought out backup system will.

 

For small NAS units, I agree with itGeeks that RAID5 is generally what people will use. Maximum capacity whilst having some redundancy is what will be picked in the vast majority of cases. For a 4 drive NAS, the safest solution in terms of redundancy is actually RAID6 since any 2 drives can fail and you're still protected. You take a severe performance penalty for using it though with the additional parity calculations and the very small number of spindles in your system. You also have to balance it with the risk during intensive rebuild process as several people have mentioned.

 

For actual servers, I use RAID6 with a hot spare and have a daily incremental backup with a weekly full backup. The array controller has a large NV cache and there is a tiered SSD cache running on top as well. I recently setup a small 10 drive server with 2.5" 15K RPM SAS drives and 1TB of NVMe SSDs. I get 900MB/s throughput for something that isn't in the SSD cache. Once data is in the SSD cache however, read requests are 1.5GB/s together with the latency and seek time benefits. It is running ESXi and it is all done by the RAID controller and ESXi itself which means it completely transparent to the VMs themselves.

 

In the long term, other technology such as ZFS will start to become more prominent as there are several benefits over RAID such as fixing the RAID5 write hole and continual self scanning with the ability to self heal.

All true, but RAID 5 or 6 require a lot of CPU, disk activity and time to rebuild. Most small NAS boxes don't have the CPU to support timely rebuilds of either parity based RAIDs 5 or 6. RAID6 on a 4 drive array gives you 50% available storage and two drive redundancy. RAID10 gives you 50% available storage and one drive redundancy or two drive redundancy as long as the two failed drives are not in the same group. Comparison between RAID 10 versus RAID 0+1:

http://serverfault.com/questions/145319/is-there-a-difference-between-raid-10-10-and-raid-01-01

If you only have four drives people lean toward RAID5 to get the most capacity. To your point RAID6 guarantees against two drive failures, but requires lots of CPU and drive activity to rebuild. RAID10 is light on the system and give you 1-2 drive redundancy. I get concerned that RAID5 or 6 on a small NAS leads users to a false sense of security. I hear of more and more cases of a second drive dying during a RAID5 rebuild. As drives get bigger this issue gets worse. 4TB drives are about as big as I would use on a RAID5 in a small 4 disk NAS. 5-6TB drives on a good RAID controller in a server for RAID5. Any drives bigger than that or more than 4 in a set, I would go RAID6 or 10 on a really good RAID controller.

IMHO

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itGeeks

All true, but RAID 5 or 6 require a lot of CPU, disk activity and time to rebuild. Most small NAS boxes don't have the CPU to support timely rebuilds of either parity based RAIDs 5 or 6. RAID6 on a 4 drive array gives you 50% available storage and two drive redundancy. RAID10 gives you 50% available storage and one drive redundancy or two drive redundancy as long as the two failed drives are not in the same group. Comparison between RAID 10 versus RAID 0+1:

http://serverfault.com/questions/145319/is-there-a-difference-between-raid-10-10-and-raid-01-01

If you only have four drives people lean toward RAID5 to get the most capacity. To your point RAID6 guarantees against two drive failures, but requires lots of CPU and drive activity to rebuild. RAID10 is light on the system and give you 1-2 drive redundancy. I get concerned that RAID5 or 6 on a small NAS leads users to a false sense of security. I hear of more and more cases of a second drive dying during a RAID5 rebuild. As drives get bigger this issue gets worse. 4TB drives are about as big as I would use on a RAID5 in a small 4 disk NAS. 5-6TB drives on a good RAID controller in a server for RAID5. Any drives bigger than that or more than 4 in a set, I would go RAID6 or 10 on a really good RAID controller.

IMHO

Great info and very well said. I have also learned a thing or two with this great conversation :)

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schoondoggy

Great info and very well said. I have also learned a thing or two with this great conversation :)

We still need to talk about drive scrubbing, prediction of failure and data destaging!  :)

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jmwills

We still need to talk about drive scrubbing, prediction of failure and data destaging!  :)

and backups.....I'd be willing to bet that 90% of the people with home RAID environments have no backup solutions.

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schoondoggy

and backups.....I'd be willing to bet that 90% of the people with home RAID environments have no backup solutions.

Unfortunately, I think you are correct. RAID adds a degree of redundancy, but it is not a backup.

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