What is Raid0?Raid1?Raid5

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Jul 20, 2018
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NAS and DAS support configure Raid

Raid0/Raid1/Raid5 are used frequently

So What is Raid0?Raid1?Raid5
 
Jul 20, 2018
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RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard disks to protect data in the case of a hard drive failure

RAID 0: This configuration has striping. It offers the best performance, but no fault tolerance

RAID 1: Also known as disk mirroring, this configuration consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage

RAID 5:The array's architecture allows read and write operations to span multiple drives. This results in performance that is usually better than that of a single drive, but not as high as that of a RAID 0 array. RAID 5 requires at least three disks, but it is often recommended to use at least five disks for performance reasons
 

asoroka

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If you are using big disk 3TB plus you have a high chance of a second disk failure while you are still rebuilding a failed array.

Enterprise grade will have Non-recoverable Read error Error every 10^15 bits read. (consumer grade will only be 1^14, so 10 times more likely to fail).

Write performance is compromised, the more disks the greater the hit. For each change to disk we need to read all data chunks plus the parity, recalculate the parity and then write all chunks back.

If you must use RAID 5 then buy enterprise grade disks that have a better unrecoverable error rate.
If you can't afford enterprise then go for NAS grade as they have better vibration tolerance so you can have many in the same enclosure.

For any RAID array, try not to get disks from the same batch, so buy them over time and from different vendors. Replace them one by one before they fail.

Remember that RAID is no substitute for backup.
 

RealBeast

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First rule of RAID -- have a complete backup since it is only fault tolerant storage (except RAID 0 which is no fault and rarely useful since SSDs became available).

I usually use enterprise drives (HGST He8 mainly) for RAID 5 arrays, the writes on RAID 6 are just to slow for most things I do. That said, I did use HGST 3TB 7200rpm consumer drives in the past for years without incident in RAID 5 (8 drives) with a hot spare and good backup. Never had a URE with hundreds of drives over many years but they can happen, hence the essential need for backup.

IMO the real issue with RAID is the quality of the controller -- no motherboard controller should be considered at all reliable, any bios hiccup and poof all gone. That is a very common storage forum problem.

Adaptec/LSI/Areca controllers are the way to go. If you can't afford that, you really don't need hardware RAID, simply use Windows Storage Spaces.

If you have the time and inclination, FreeNAS using RAID-Z is also a very viable alternative but it does require a dedicated box to run.
 
New disks r/w around 1Gbs a second. If you have 1Gbs network then there is no point for stripes. raid1 with 2disks will save you money. raid 5 is used for a 2nd or 3rd tier hot backup because it has more usable space. if you lose a 3rd tier backup it's not a total loss. raid 1 or 10 gets expensive in a big data center. big companies will mirror their data over separate geographic regions have multiple hot backups and cold ones.

You can backup an entire pc on backblaze(online) for $95/2yrs. it's not immediately available if you need it.
other cloud providers like dropbox or google drive cost a lot more per GB.
 

RealBeast

Titan
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That is only close to true if you are reading a single large sequential file, otherwise it is pretty much completely wrong.

 


I said no point for stripes, which hurt your randoms....
 
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