Which raid to use

Since parity must be calculated whenever the drive is written to, write performance is reduced. The problem is amplified when you take into consideration the fact that flipping a single bit in one drive requires all the drives to be read from in order to recalculate parity for that block. Also, no matter how many drives you have, you can only survive one drive failure.

This allows your array to survive two drive failures. However, write performance is worse at n - 2 , and you will of course have less space. RAID 6 alone fulfills the first part of the backup strategy —store at least three copies of your data, with two backups on different media, with at least one of those located offsite.

In practice, RAID 6 will almost never experience a total array failure, especially if you add more parity disks into the equation. This, combined with backups and copies in other datacenters, is how archive services like AWS Glacier and Backblaze achieve RAID 10 requires at least four drives, and also requires an even number of total drives.

This gives you all the benefits of RAID 1 and RAID 0 without many downsides—fast read speeds, fast write speeds, high redundancy, and easy rebuilds, while still being able to use half of the total space of all of your drives. In the diagram above, Disk 1 and Disk 3 could fail, and the array could still be fully rebuilt though if both Disk 0 and Disk 1 fail, that array is unrecoverable. This improves performance just like RAID 10, most importantly improving write performance, since reading from the other drives when calculating parity is faster.

The above article may contain affiliate links, which help support CloudSavvy IT. Skip to content Cloud Docker Microsoft. Linux Cybersecurity Programming. Popular Searches Cloud Docker Microsoft. Whether to deploy RAID depends mostly on how important uptime is to your operations. If staying online is essential, RAID is your failover insurance. Without RAID installed, your server and business will suffer downtime while the drive is being reconfigured and replaced. Then backups need to be restored; all this could take 5 or more hours easy.

With RAID installed, the drive would be replaced, and you could rebuild and sync the RAID from the old drive to the new drive, and there would also be no backup restoration required.

This provides optimal performance, as the processing is handled by the RAID card rather than the server, providing less strain when writing backups and restoring data.

This is the cheaper option; all you need to do is connect the drives and configure the OS. Here is a very simple TLDR chart. Read on for a more detailed version of the pros and cons of each. Your dedicated server loses power before changes have left the cache and committed to disk, resulting in corrupted data. The contents on the RAID card become unrecoverable and you may not know what files are damaged.

Essentially, a BBU is a data fail safe. Usage: Ideal for database servers and any environment with many small random data writes. Up to one drive in each sub-array may fail without loss of data. Also, rebuild times are substantially less than a single large RAID 5 array.

A RAID 50 configuration can accommodate 6 or more drives, but should only be used with configurations of more than 16 drives. It should be noted that you can have more than two legs in a RAID The first of these two arrays would offer greater capacity as only two drives are lost to parity, but the second array would have greater performance and much quicker rebuild times as only the drives in the leg with the failed drive are involved in the rebuild function of the entire array.

Usage: Good configuration for cases where many drives need to be in a single array but capacity is too large for RAID 10, such as in very large capacity servers. Dual parity allows the failure of two drives in each RAID 6 array while striping increases capacity and performance without adding drives to each RAID 6 array.

Usage: RAID 60 is similar to RAID 50 but offers more redundancy, making it good for very large capacity servers, especially those that will not be backed up i. We can classify data into two basic types: random and streaming.

Random data is generally small in nature i. This is typified by database-type data. Streaming data is large in nature, and is characterized by such data types as video, images, general large files.

Having these two different arrays spanning the same drives will not impact performance, but your data will benefit in performance from being situated on the right RAID level. This should be checked carefully with the product specifications from the drive vendor to make sure you are getting the performance you think you are getting from your drives. With HDDs it is generally better to create an array with more, rather than fewer, drives.

With SSDs, however, it is advisable to achieve the capacity required from as few as drives possible by using larger capacity SSDs. These will have higher throughput than their smaller counterparts and will yield better system performance. It is a little-known fact that you do not need to use all of your drive capacity when creating a RAID array. When, for example, creating the RAID array in the controller BIOS, the controller will show you the maximum possible size the array can be based on the drives chosen to make up the array.

During the creation process, you can change the size of the array to a lesser size. The unused space on the drives will be available for creating additional RAID arrays. A good example of this would be when creating a large server and keeping the operating system and data on separate RAID arrays. This would use a minimal amount of capacity from each drive. You can then create a RAID 5 for your general data across the unused space on the drives. This has an added benefit of getting around drive size limitations for boot arrays on non-UEFI servers as the OS will believe it is only dealing with a GB drive when installing the operating system.

The more drives in the array, and the larger the HDDs in the array, the longer the rebuild time when a drive fails and is replaced or a hot-spare kicks in. While it is possible to have 32 drives in a RAID 5 array, it becomes somewhat impractical to do this with large spinning media.

When a drive fails and is replaced, only 16 of the drives 15 existing plus the new drive will be involved in the rebuild. This will improve rebuild performance and reduce system performance impact during the rebuild process.

In a real-world environment with a heavily-loaded system, the rebuild times will be even longer. Of course, rebuild times on SSD arrays are dramatically quicker due to the fact that the drives are smaller and the write speed of the SSDs are much faster than their spinning media counterparts.

However, you may need test whether enabling read and write cache will improve performance even further. Note that it is possible to disable and enable read and write cache on the on the fly without affecting or reconfiguring the array, or restarting the server, so testing both configurations is recommended.

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All other trademarks and service marks are the property of their respective owners. Audio, Voice, and Line Circuits Software. Audio, Voice, and Line Circuits Documents. MyMicrosemi Partner Portal. PoE Support Cases. PoE Collateral. Storage ICs Documents and Software. Timing ICs Documents. What is RAID? Mirroring RAID 1 replicates data on two drives, preventing loss of data in the event of a drive failure.

When a failed drive is replaced, the lost data is rebuilt from the remaining drives. Hardware RAID vs. How does RAID work? Who should use RAID? Pros: » Fast and inexpensive.