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SSD Cache Limits?

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I would like to build a Home Storage Server,

 

5 x 8TB WD Red Drives (1 drive for parity, 4 for storage)

1 x 500GB SSD For cache

 

I will be using my Macbook Pro as Plex Server, with the Unraid Server selected as Storage Location. 

 

1) What is the recommended Rack Server Build Specs I should go for. 

2) I won't be keeping the server on 24hours a day, would turn the server on only when I want to use Plex or dump some data onto the server. Which would be typically 2 to 3 hours a day. My main query is, how long does it take for the server / array to restart everytime I boot, assuming 32TB of used disk space. 

3) Lastly, I would like to know the transfer speeds. I have read across forums that the transfer speeds are about 40MB/s on a Gigabit ethernet connection, things speed up to about 100MB/s if we use SSD for cache. However, the data that is dumped to the SSD gets transfered to the drives at a fixed time in a day, is it possible that the data gets transferred from SSD Cache Drive to the HDD drives just after a minute ?

4) I will be having a 500GB SSD for Cache. Once I build the server, I would like to dump around 25TB of data onto it. If I transfer more than 5TB at a time, what are the limitations of the cache drive, and is there a work around it?

Consider if you really want a rack server build - they tend to be noisy and are best when you already have lots of other equipment. Or when you really need to fit a huge number of drives. With just 5x 3.5" disks and a single 2.5" cache drive you have lots of less noisy options than a rack build.

 

If your goal is to copy files to the system and then turn off, then you are better off not involving a cache drive. It will not go faster to copy to a cache drive first and then copy from cache to disks. Turn on turbo write and copy directly to the array.

  • Author

Thanks for your input. I would like to point out that my build is not limited to just 5 drives, It is the data that I have accumulated until now.

 

I am planning to add more rack server in future, as and when required. I am adding about 2tb data a month at the minimum. So probably a 1U Rack server with 4 drive bays (6tb drives), each year. Don't want to have a lot of Towers lying around. 

 

I would appreciate if you could give insight to "how long does it take for the server / array to restart everytime I boot, assuming 32TB of used disk space".

A number of towers can handle 12 3.5" drives. More if using 5-in-3 trayless inserts where you fit 5 3.5" disks in the space of 3 5.25" slots.

 

If you are adding 2 TB / month, that's still just 24 TB / year. So 3x 8 TB disks or 2x 12 TB disks. And they are regularly releasing larger drives.

 

Your life will not become easier if you have your data spread over multiple machines, having a lot of rack servers lying around ;)

 

Multiple servers are best when used for very different things or when having secondary servers for backup.

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