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RAID level 0 and 1

phman1275 used Ask the Experts™
RAID levels 0 and 1 can be combined to make a stripe of mirrors (RAID 10) or a mirror of stripes (RAID 01) configuration.  Which implementation would you prefer to use and why?
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RAID0 is just striping, you get the full disk capacity, it is very fast, but with no redundancy; a single drive failure means all data gone. Only used when a cheap, fast drive is required, and it does not matter much if it unexpectedly dies. Temporary storage on a workstation used for editing video might use this.

RAID1 is mirroring, everything is copied onto to two drives.  Fault redundant, but performance is comparable to that of a single drive. Used where performance is not critical, but availability is. This is commonly used for a small boot drive on a server, it may for example use a paid of 128Gb SSDs.

RAID10 is a combination. It is used where both performance and availability are important. Needs a minimum of 4 drives. This is commonly used for actual data storage on servers, so this is where shared files, Exchange or SQL data is usually kept.

RAID5 is also worth a mention, this was more popular in the past, but less common now. It has moderate performance, but can be slow writing large numbers of small files. It has the advantage of only loosing the capacity of a single drive, 6 1Tb drives in RAID5 gives 5Tb of useable capacity, rather than 3Tb that RAID10 would offer. With modern drives however, sometimes when a single drive fails, the increased load on the others during a long rebuild can result in lost data. This has limited use in 2019, I still use this for large, cheap drive volumes for disk-disk backups.

So, to answer your question, "It depends".  A single server might be set up with RAID1 for the boot volume, RAID10 for data storage, and copy off to another server running RAID5 for backups.
Network Engineer
There is a huge difference between RAID 10 and RAID 01. The difference is reliability, in that in a large array a RAID 10 can possibly lose 50% of disks and still be operational, and a RAID 01 has a greater than 50% chance of failing completely with only 2 dead disks.

I would never use RAID 01. Always RAID 1, 10, 5, 6, or 60, depending on type, number, and size of disks and the storage workload.1

See this for a good representation.


Thank you!