RAID 1 Drives

[koalaroo]

Theoretical situation here;

If I had one 500GB SSD set up in RAID 1 with one 500GB HDD, would the SSD's speed be limited to that of the mechanical hard drive? Is this setup even a possibility in RAID?

[DrM]

yes and yes. in raid 1, data has to written to both drive at the same time, so both would be limited to the hdd speed

[koalaroo]

Just now, DrM said:

yes and yes. in raid 1, data has to written to both drive at the same time, so both would be limited to the hdd speed

Thought so. Was hoping I could cheap out and have a safe backup like that with performance somewhere in between.

[Mark77]

In a writes scenario, yes, you would be limited to the fastest of the two devices.

 

In a reads scenario, a RAID-1 can be set up to read from a single drive (ie: the SSD) almost exclusively.  Or the system can balance the load between the two devices. 

 

Obviously if you're RAID-1'ing a SSD to a HDD, you would want to set the system up to "prefer" the SSD.

 

In Linux RAID-1, you do this by setting the "write-mostly" flag.  Per: http://tansi.info/hybrid/

[Captain_WD]

6 hours ago, koalaroo said:

~snip~

Hi there

 

Generally you can put any two or more drives in a RAID array with the proper settings and controllers. When it comes to simple SATA HDDs or SSDs the answer is YES, you can use them in the same RAID array, but it's not really recommended nor safe for your data. The speed of the SSD will be limited to the one of the HDD since RAID generally limits all drives' speeds to the one with the slowest and the capacity to the one with the smallest. 

 

You can configure a continuous backup with an application from the SSD to the HDD and thus have everything backed up there instead of mirrored.

 

Captain_WD.