Southbark Posted January 1, 2017 Share Posted January 1, 2017 I have a lian-li pc-q25 build happening just waiting on a part to put in psu. I have 2 3tb wd red drives and 3 1tb drives to start with. I understand the concept of a parity drive but not sure about size and wether I need two of them or not Quote Link to comment
Helmonder Posted January 1, 2017 Share Posted January 1, 2017 The parity drive needs to be at least as large as your largest data drive. Your data drives are 3TB so your parity should be at least 3 TB. Know that when you add a new drive in the future you cannot use a drive larger then your parity drive. So lets say you want to expand your array in the future and you want to add a 6TB data drive, then you would need to add 2 6TB drives, one for parity and one for data. Your current parity drive you can then reuse as a data drive. As far as 1 or 2 parity drives is concerned, that is up to you. With one parity drive one disk can fail and you loose nothing. With two parity drives you can loose two. Quote Link to comment
Southbark Posted January 1, 2017 Author Share Posted January 1, 2017 As far as 1 or 2 parity drives is concerned, that is up to you. With one parity drive one disk can fail and you loose nothing. With two parity drives you can loose two. How do you lose 2 drives if one fails? Can I buy just one big parity drive 6 or 8 tb to cover the whole system? For future upgrades Quote Link to comment
trurl Posted January 2, 2017 Share Posted January 2, 2017 As far as 1 or 2 parity drives is concerned, that is up to you. With one parity drive one disk can fail and you loose nothing. With two parity drives you can loose two. How do you lose 2 drives if one fails? What he meant is that if you have 2 parity drives, you can have 2 disks fail simultaneously and you still loose nothing. Can I buy just one big parity drive 6 or 8 tb to cover the whole system? For future upgrades If you have a 6TB parity drive then you can use any number of data disks* but no single data drive can be larger than 6TB. Similarly with 8TB parity, any number of data disks but none larger than 8TB. So the size of the parity drive doesn't limit how much storage you can have, it just limits how large any single drive in your storage can be. Of course there are other limits such as number of ports, number of drive bays, number of connections allowed by your license. *Technically there is some limit to the number of disks you can assign to the array even with a PRO license. (is it still 26?) Quote Link to comment
tdallen Posted January 2, 2017 Share Posted January 2, 2017 As far as 1 or 2 parity drives is concerned, that is up to you. With one parity drive one disk can fail and you loose nothing. With two parity drives you can loose two. How do you lose 2 drives if one fails? Can I buy just one big parity drive 6 or 8 tb to cover the whole system? For future upgrades You might want to read this: http://lime-technology.com/wiki/index.php/UnRAID_6/Overview#Parity-Protected_Array A single parity drive can protect any number of data drives, up to the 28 drive limit of a Pro license (mind you, I'd have added the 2nd parity drive long before then ). The parity drive doesn't need to get bigger as you add more drives - it just needs to be as big as your biggest data drive. If you'd like to add 6TB or 8TB data drives in the future then by all means, invest in a 6TB or 8TB parity drive now. Quote Link to comment
Raja Ray Posted January 16, 2019 Share Posted January 16, 2019 (edited) If I want to use two parity disk and three data disk than data will be safe or not..? Edited January 16, 2019 by Raja Ray Quote Link to comment
Raja Ray Posted January 16, 2019 Share Posted January 16, 2019 Whats Size I will use for cache disk for NAS? Quote Link to comment
Hoopster Posted January 16, 2019 Share Posted January 16, 2019 13 minutes ago, Raja Ray said: If I want to use two parity disk and three data disk than data will be safe or not..? Parity disk(s) protect against disk failures, They DO NOT contain a backup of the data. If you have two parity disks and three data disks in your array, two of the three data disks (or one parity and one data disk) could fail at the same time and the data will be rebuilt on replacement disks when they are added to the array. You still need to make backups of your important data to storage outside of the array such as external drive(s) a backup server, the cloud, etc. Quote Link to comment
Hoopster Posted January 16, 2019 Share Posted January 16, 2019 29 minutes ago, Raja Ray said: Whats Size I will use for cache disk for NAS? I depends on what you will use it for. Will you cache writes to the array? Store your docker applications in appdata on the cache drive? Save downloads to cache? You need to decide what you will use the cache drive for and size it appropriately for those needs. Most have cache drives (if they are SSDs which is recommended) between 250GB to 1TB in size. You may also have more than one cache drive in a cache pool. Quote Link to comment
Joseph Higgins Posted March 2, 2023 Share Posted March 2, 2023 What I don't see anything talked about is time. If you are putting in large drives 10-18TB and have an 18TB parity drive it will take months for the parity to be created. If you lose a drive, (which I have not yet) I assume it will take just as long to rebuild the files. For things like family pictures, maybe you can wait months. For things like VM's or web application files, you need those back IMMEDIATELY. So best thing to do is create multiple backups of the files, and a cloud offiste backup too. Quote Link to comment
JonathanM Posted March 2, 2023 Share Posted March 2, 2023 4 minutes ago, Joseph Higgins said: an 18TB parity drive it will take months for the parity to be created If everything is healthy, 48 hours at most. Probably closer to 24 hours. I assume you were being hyperbolic when you say months. Quote Link to comment
JonathanM Posted March 2, 2023 Share Posted March 2, 2023 8 minutes ago, Joseph Higgins said: I assume it will take just as long to rebuild the files. Parity works in realtime, so the emulation of a failed drive is realtime, you have access to all the files while the failed drive is being rebuilt as well. No waiting. Quote Link to comment
Joseph Higgins Posted March 2, 2023 Share Posted March 2, 2023 Maybe something is wrong with my system? It was showing 365 days this morning. Can I expect it will keep dropping? At 1MB/second it will take a long time to chew through 14 TB I assume. Quote Link to comment
Joseph Higgins Posted March 2, 2023 Share Posted March 2, 2023 Interresting, keeps dropping. Maybe speeding up in the unused space? I would not think it would matter much since it has to calculate every bit across all drives in the array. Quote Link to comment
Joseph Higgins Posted March 2, 2023 Share Posted March 2, 2023 I had just added the 14 TB Parity and 2 additional 14 TB drives in the array yesterday. Quote Link to comment
JonathanM Posted March 2, 2023 Share Posted March 2, 2023 If anything is writing to the array drives it slows down the parity build significantly to keep the array accesses as quick as possible. Click the blue lines icon at the top right of your large screenshot to show drive speeds instead of access counts. That may help you figure out what is accessing the array. Quote Link to comment
Joseph Higgins Posted March 29, 2023 Share Posted March 29, 2023 I ended up turning off all the writes (downloads) to the array while parity was building. For the size of the array it took 2 days to build. Strangely, the parity build would crash any dockers, even though they were on the cache drive. So I also had to disable docker during the parity build. If there were a rebuild of parity, I would not want to have to stop Docker. This is keeping me from using it in a production environment. Quote Link to comment
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