RAID Array Servers Dos & Don'ts | RAID Best Practi – TechMikeNY
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RAID Do’s and Don’ts

RAID Do’s and Don’ts


At TechMikeNY, a big part of what we sell are Enterprise rack servers.  A big part of servers is RAID.  (If RAID is a new concept to you, read our blog post here, which is a handy primer.)  Since so many of our customer questions revolve around RAID configurations and trouble-shooting, we thought it would be a good idea to put down some typical RAID array server Do’s and Don’ts which can serve as Best Practices.


Do NOT mix SSDs And HDDs in the same RAID virtual disk. 
SSDs offer flash technology speed, but traditional HDD drives still provide a better price per MB.  Which is right for you?  That depends if you want your RAID disk to have an emphasis on speed vs. volume.  However, unfortunately, due to the entirely different read and write methodologies of SSDs and HDDs, you cannot have them in the same RAID risk.
(P.S., we like this summary of SSDs and HDDs in RAID if you are curious to learn more). 

Do NOT mix SATA and SAS drives in the same RAID virtual disk. 
SAS interface hard drives are more reliable and faster than their more ubiquitous SATA interface cousin.  However, a SAS drive costs approximately 10% more than a SATA drive, as of this writing.  Which is right for you again depends on your needs – budget vs. performance.  While the vast majority of rack Enterprise servers that TechMikeNY sells have backplanes that can take both SATA and SAS interface drives, you cannot have them mixed in the same RAID virtual disk. 
(If you want to read more about SAS vs. SATA, our blog post here covers the basics as well as other compatibility pitfalls.)

Do NOT Mix Advanced Format Drives (AF) 4Kn with Non-AF/512n drives
To take advantage of the advances in hard drive technology, manufacturers have started producing higher density drives.  The result is hard drives that utilize more of their volume for your data (and not partitions or spaces in the drives’ sectors to check the data). 
These drives are branded as “Advanced Format” (AF) and are divided into two sub-groups: 512e and 4Kn.  4Kn drives have 4,000 bytes per logical and physical sector; 512e (e = emulation) essentially tricks or “emulates” the logical sector into being read as a traditional 512n (n = native) sectored drive.  Lenovo has a comprehensive white paper here that gives an excellent overall summary; you can also read our blog post here, which goes more in-depth on Advanced Format drives.   
The key point: do NOT mix 4Kn drives with traditional 512n drives (non-AF) in the same RAID disk.   As for mixing 512e drives and non-AF drives, it is possible, but we don’t recommend it – you could have alignment issues between the drives that affect performance (even if it is functional). 

 HOT TECH TIP: Dell 12th Gen Servers and H.P. 8th Gen Servers – and prior generations – do not work with 4Kn drivers. 


DO set-up redundancy with your RAID disk
We could go on and on about the importance of back-ups (and we have, as you can read here!), but always remember to follow proper back-up best practices and avoid RAID 0 configurations since there is no back-up in place. 

DO Keep all the drives the same in your RAID disk
The expression “a chain is only as strong as its weakest link” is apropos when thinking of RAID.  Be sure to have drives in a RAID virtual disk that are the same speed and same volume.  Drives with different size volumes in a RAID disk will all default down to the drive with the smallest volume; HDDs with different RPMs – e.g., 10K vs. 15K – will default to the slower speed. 
Save yourself the aggravation and keep all the disks in the RAID configuration the same!

 DON’T FORGET!  If you already own a server from us and want to add drives, make sure you have the caddies available for those drives. And if you are unsure which caddies you need, reach out.  That’s what we’re here for!

You CAN have different types of drives, with different Interfaces, in the same server – just not in the same RAID disk.
We’ve discussed how you cannot have different disks – type and interface – on the same RAID disk. However, you can have multiple RAID disks in a single server, and those disks can be different between the V.D.’s.  For example, a 10-Bay server could have two SAS SSDs configured in RAID 1 with an O.S. installed for speed, and then the remaining eight free bays loaded with SATA HDDs in RAID 5.  Provided the disks within the RAID disk are matching, then you should have no issues. 
Do you have more questions on RAID?  Questions on anything server and tech-related? Let us know!  Shoot us an email at, and we’ll happily answer and maybe even cover it in our blog!

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