Parity drive: latency or bandwidth?

[nosro]

I have two existing 1tb drives:

1) Samsung: has superior sequential read/write speed, but inferior random access performance

2) WD black: has superior random access read/write speed (including superior simultaneous read and write performance), but inferior sequential performance

 

Which one is better suited to being a parity drive?

[BRiT]

It depends on your access/usage patterns.

 

Do you do more writes to multiple drives or mostly to a single drive?

[nosro]

I usually write to a single drive at a time.

[WeeboTech]

I have two existing 1tb drives:

1) Samsung: has superior sequential read/write speed, but inferior random access performance

2) WD black: has superior random access read/write speed (including superior simultaneous read and write performance), but inferior sequential performance

 

Which one is better suited to being a parity drive?

 

Sequential write speed is important when you are loading data.

When you are reading Sequential or Random, the parity drive is hardly used.

So minimize that in your calculations.

 

If you are just doing movie/media storage then the fastest sequential access patterns are important.

 

In my case I do very general file server usage and it could be to more then one drive. so simultaneous read and write performance is a big factor.

 

I've noticed with the Samsung F3 1tb's they write at 80MB/s but can read at up to 150MB/s. I believe it's how the cache algorithm is set.

Keep in mind every write, starts out as two reads, then two writes.

 

I have no experience on the WD Blacks so I cannot comment there.

 

On the Seagate 1.5tb's I get around 80-100MB writes and 125MB reads.

Once parity comes into play that drops to about 30MB/s writes.

[nosro]

 

Sequential write speed is important when you are loading data.

When you are reading Sequential or Random, the parity drive is hardly used.

 

 

So when reading, the parity drive is used only when the data disk indicates errors. Is this correct? (I had thought the parity was always read to "check" the integrity of the data disk.)

[neilt0]

 

Sequential write speed is important when you are loading data.

When you are reading Sequential or Random, the parity drive is hardly used.

 

 

So when reading, the parity drive is used only when the data disk indicates errors. Is this correct? (I had thought the parity was always read to "check" the integrity of the data disk.)

 

Correct to the former. If you are only reading data and not writing, the parity drive will be spun down after it idle times out.

[bubbaQ]

(

I had thought the parity was always read to "check" the integrity of the data disk.)

 

Parity alone can not tell you anything about data integrity... you have to calculate the parity by spinning up ALL the disks, and then check the parity if you want to do that.