I am building a new server to act as a media server - mainly running SageTV and acting as a file server.

 

Is it worth paying a bit of a premium to get the PCIe4 M.2 NVME drives vs the previous generation to act as cache drives?  I am thinking that the speed is probably worth the premium, as it seems that these drives are at least 30% or so faster.  I will likely have an Intel 11th Gen CPU like an i5-11400 and something like an Asus B560-PLUS mobo.

...you will be able to leverage this advantage only if your platform supports PCIe gen. 4 (and if the choosen nvme  itself can deliver a datarate higher than bandwidth of PCIe gen.3, see: https://en.wikipedia.org/wiki/PCI_Express#History_and_revisions ).

On this particular MB, only the first M.2 slot is PCIe gen. 4, while the second one is PCIe  gen. 3

In general, a PCIe gen.4 advertised nvme will be backwards compatible to a PCIe gen 3 connection/slot.

Personally, I'd not recommend to mix and match specs, although it will technically work. 

 

Edit: also note, that you probably need some more advanced parts in your network infrastructure to actually leverage that performance for clients.

While a Docker container, transcoding media between local shares/disks can be as fast as the CPU or Disk allows, even a 10G network link is limited to 1GByte/sec, whilst that piece of storage can sustain 2-4times as much.

Delivering the same, concurrently, meaning 2-4GByte/sec transcoding and delivering approx 40+Gbps to clients will be well beyond the capabilities of your platform, I think.

 

Edited December 13, 20214 yr by Ford Prefect

Thanks, it looks like the motherboards that I am looking at, like an Asus Prime B560-PLUS have one M.2 slot that is gen 4 and one that is gen 3. I would be looking to pair that with an 11th gen Intel CPU as I mmentioned in the original post, and that CPU does support gen 4.

 

If I were to use the M.2 NVME drives in a dual cache framework would I get the advantage of the higher speed or does the RAID methodology, or whatever is used to give redundancy on a cache drive, mean that I am limited to the slower speed.

 

But the bigger issue that you raised, which I had not considered, is that the bottleneck may be my network.  Pulling UI elements from the appdata folder, which will be on the Cache drive(s), to my clients in something like SageTV or Plex will likely be bound by the network speed, although in the past when I went from mechanical hard drive to SSD there was a noticeable increase in speed.  Is that the case?

 

What about having VMs on the Gen 4 vs Gen 3.  Would I have a noticeable increase in speed?

3 hours ago, wayner said:

If I were to use the M.2 NVME drives in a dual cache framework would I get the advantage of the higher speed or does the RAID methodology, or whatever is used to give redundancy on a cache drive, mean that I am limited to the slower speed.

Using a cache pool in raid1 btrfs is for redundancy, not speed.

The two disks in the pool are stil not striped, just mirrored and if the two disks are of different speed/performance, the raid/redundancy will be somewhat lagging behind until the data is written two both disks completely.

I actually have no experience if the performace of a client will be that of the disk the client is writing to/reading from or that of the pooled device (which would keep both disks in the pool in sync, resulting to the slower speed of the two). When reading data, this is the same I think. However, when service i.e. two clients concurrently, each client could be served from either one od the two disks.

Again I do not know how this software raid mechanism of btrfs will behave.

 

3 hours ago, wayner said:

But the bigger issue that you raised, which I had not considered, is that the bottleneck may be my network.

Yes, since a gen.3 PCIe nvme can perform 2-3time faster than a 10G network, this will be your bottleneck. A gen.4 nvme will not perform faster in that case.

 

3 hours ago, wayner said:

Pulling UI elements from the appdata folder, which will be on the Cache drive(s), to my clients in something like SageTV or Plex will likely be bound by the network speed, although in the past when I went from mechanical hard drive to SSD there was a noticeable increase in speed.  Is that the case?

Yes, a HDD can deliver 1-2.5 Gbps, a SSD up to 6 Gbs ... so there is an increase with SSDs already but the performance of a single 6Gbps SSD will still only half saturate a 10Gbps network link. With a 1Gbps network link, even a SSD is an "overkill".

A gen.3 PCIe nvme will at least outperform a 10G link by factor of two...so, while delivering 4 times the bandwidth of a SSD only an increase of factor two over network.

 

 

3 hours ago, wayner said:

What about having VMs on the Gen 4 vs Gen 3.  Would I have a noticeable increase in speed?

Locally, a gen.4 nvme can be much faster than a gen.3 and of course a VM will notice the difference. However for VMs the IOPS are more importand than throughput. So look at the specs of the device in question.

I do have a cache pool of two of these: https://www.corsair.com/de/en/Categories/Products/Storage/M-2-SSDs/Force-Series™-Gen-4-PCIe-NVMe-M-2-SSD/p/CSSD-F1000GBMP600

Although being gen.4 PCIe, my platform only allows for gen.3 ... but they had a lower price and better IOPS and TBW than the gen3 counterpart at the time i bought them.

As they are backwards compatible, there was nothing to loose buying them.

Thanks  Ford, that is very useful stuff.  I owe you a pan galctic gargle blaster!