davidst95 Posted October 31, 2019 Share Posted October 31, 2019 Hi, I have four 10GB WDC Red HDDs. Is it overkill to have two parity drives for just four drives? I don't think I would need more than 20TB of space. I will also be using two 500GB SSDs for cache. Thanks! David Quote Link to comment
JonathanM Posted October 31, 2019 Share Posted October 31, 2019 Do you have full backups of all important data already in place and a strategy to keep them updated? If not, then the extra drive would be much better as a backup drive. Parity will help with keeping your array up and running when a drive fails, and dual parity can be valuable if you have a second failure while you are rebuilding the first failure, but it won't get deleted or corrupted files recovered. Only backups can do that. Quote Link to comment
testdasi Posted October 31, 2019 Share Posted October 31, 2019 9 hours ago, davidst95 said: Hi, I have four 10GB WDC Red HDDs. Is it overkill to have two parity drives for just four drives? I don't think I would need more than 20TB of space. I will also be using two 500GB SSDs for cache. Thanks! David Your statement is a little confusing. It can mean 2 things: 2x data drives + 2x parity drives = 4x 10TB that you have. 4x 10TB data drives + 2x parity drives (to be purchased) If it's (1) then you are better off with a single parity and use the other drive as a backup for your most critical data. If you already have a backup solution in place then 3x array + 1x parity should be sufficient. If it's (2) then it's less clearcut. Based on backblaze HDD failure stat, I estimated that the "reasonable break-even point" (defined by me as when the expected rate of failure is not higher than the number of parity) for a dual-parity is still higher than 6 drives (i.e. 4 data, 2 parity). It is even higher if we only consider stat for only 8TB+ drives - which even Backblaze observed that they didn't seem to fail as often. However, I can see merit of dual parity for the very risk-averse - after all HDD failure is a probability thing. Quote Link to comment
davidst95 Posted October 31, 2019 Author Share Posted October 31, 2019 8 hours ago, testdasi said: Your statement is a little confusing. It can mean 2 things: 2x data drives + 2x parity drives = 4x 10TB that you have. 4x 10TB data drives + 2x parity drives (to be purchased) If it's (1) then you are better off with a single parity and use the other drive as a backup for your most critical data. If you already have a backup solution in place then 3x array + 1x parity should be sufficient. If it's (2) then it's less clearcut. Based on backblaze HDD failure stat, I estimated that the "reasonable break-even point" (defined by me as when the expected rate of failure is not higher than the number of parity) for a dual-parity is still higher than 6 drives (i.e. 4 data, 2 parity). It is even higher if we only consider stat for only 8TB+ drives - which even Backblaze observed that they didn't seem to fail as often. However, I can see merit of dual parity for the very risk-averse - after all HDD failure is a probability thing. Thanks for the reply and information. I have a total of 4x10tb drives. If I want to use the 4 drive as a backup should I add to unraid as an unassigned drive and use or write a script to transfer important data over? Thanks again! David Quote Link to comment
davidst95 Posted October 31, 2019 Author Share Posted October 31, 2019 44 minutes ago, davidst95 said: Thanks for the reply and information. I have a total of 4x10tb drives. If I want to use the fourth drive as a backup should I add to unraid as an unassigned drive and use or write a script to transfer important data over? Thanks again! David Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.