Do i “need” SSD cache pool?

[kakburken]

Im building a 24-disk (SATA 7200prm Enterprise HDD's) Unraid NAS that is only going to be used to download (save/write), store and play (read) media.

 

All the "applications", like Plex, Torrent, Radarr/Sonarr.. you name it, will be on another NAS (Synology RS1619xs+) with enterprise SSD's. So all the Unraid server will do is act like a share for all other applications to access.

 

Im planning on having 2 disks as parity in the Unraid server (doubt it matters, but i thought id mention it).

 

So, im uncertain if i "need" a SSD cache pool in unraid or not. So i was hoping i could get your input on the matter.

 

The biggest thing on my mind, and perhaps the biggest reason to creating this post, is whatever not using a SSD cache pool will greatly reduce download speeds from torrent-client since it writes to HDDs, if not using SSD cache pool.  Now, granted this was a long long time ago, i remember when i used HDD's "back in the days" and used utorrent (that was the thing back then) there was a ton of issues/errors because the drives couldnt keep up. Cant remember the actual errors (or warnings perhaps), but it had something to do with "congestions" or something and i know that at that time it was solved with using SSD's to write (download) to and then movie it to the HDD-storage.

 

So, is that still a thing? Do i need/is it recommended to use a SSD cache pool? Im pretty sure i had 7200rpm HDDs back then too..

 

Would greatly appreciate any help since im as new to this as a toddler is to the world. Its all very exciting, but also very scary and most of the time i have no clue on why things are as they are.

Edited June 29 by kakburken
typo

[Wody]

A lot of it depends on your internet-speed. If you have gigabit-internet or better you'll want to store files as fast as possible, so then cache is very useful. But if your internet is comparable to the speed of the drives, then SATA could become a blocker because it can only do one thing at a time. But then if you set unraid to store new files on different drives, you can download 24 things at the same time with full speed.

 

[kakburken]

27 minutes ago, Wody said:

A lot of it depends on your internet-speed. If you have gigabit-internet or better you'll want to store files as fast as possible, so then cache is very useful. But if your internet is comparable to the speed of the drives, then SATA could become a blocker because it can only do one thing at a time. But then if you set unraid to store new files on different drives, you can download 24 things at the same time with full speed.

 

Thanks for answering and giving me all that info!

 

 I’m using 250mbit at the moment, though I can get 1gbit connection if I want, I’m not sure I’ll ever want to pay that cost (around $70/month). If anything I’ll go down to 100mbit again. But as for now I’ll stick with 250mbit for about $42/month.
 

I’m not educated enough on Unraid yet to know if I’m going to have Unraid store new files on different drives. Don’t know the pros and cons yet. Or why you’d like to do that (or not).
 

By saying “SATA could become a blocker”, do you mean my SATA HDD's or the SSD's (cache pool)? I guess I’m not sure you mean that cache pool is a good thing if my internet speeds are comparable to the drives (I’m guessing you talk about the HDD's here) or if it’s a bad thing.

 

I might add that IF I decide to use SSD cache pool it will be SATA, and not M.2 for a couple of reasons.

 

scratch that last thing. Haven’t decided yet between M.2 or SATA.

Edited June 30 by kakburken

[_cjd_]

HDD speed may limit you slightly with 250Mb internet service. I saturate RAID10 SATA ssd on 10Gb Ethernet (internet is far slower) but just... Close enough I'm not trying to figure out how to use m.2 for SSD cache. Single drive write is obviously slower but still beyond 1Gb speeds.

 

Here's the thing though - you can always add cache later.

 

24 disks is going to be power hungry and expensive - why so many? Up against your concern over internet costs that strikes me as odd, but maybe that's just me.

[kakburken]

37 minutes ago, _cjd_ said:

HDD speed may limit you slightly with 250Mb internet service. I saturate RAID10 SATA ssd on 10Gb Ethernet (internet is far slower) but just... Close enough I'm not trying to figure out how to use m.2 for SSD cache. Single drive write is obviously slower but still beyond 1Gb speeds.

 

Here's the thing though - you can always add cache later.

 

24 disks is going to be power hungry and expensive - why so many? Up against your concern over internet costs that strikes me as odd, but maybe that's just me.

 

yes, thats right, i can add it later. just wanted to know beforehand if it was a certain yes or no. But i guess ill see what i do. perhaps ill try without first or perhaps i wont.

 

I dont feel thats odd at all. the contrary, i rather save those ~$28 every month to buy new disks (thats about a new 12TB drive every 7th month or so..).

And 250mbit (or even 100mbit) is often way more speed than you need for downloading/seeding. Its not like i sit around and wait for stuff to be downloaded and need it done within a few minutes. And i dont have the need to be that cool kid with gigabit fiber bragging about it on reddit or other forums.

 

And why i need so many? You can never get enough storage space.  that and im building myself some kind of personal/for-my-own-use streaming service with as much of the good stuff from every streaming provider possible since im sick of all the quadrillion services that costs a fortune if you want to access all (or most) of the good stuff. So until they do something like the music industry did, im showing them my middle finger (well not really) and downloading it instead.

 

(if its frown upon to talk about that stuff here let me know and ill remove that part of the answer in this post)

[Wody]

10 hours ago, kakburken said:

By saying “SATA could become a blocker”

What I mean is SATA is a great connection, but it isn't very good at doing many things at once. I'm sure you noticed, especially on windows, if you have a list of torrents, and you scroll through them while downloading some, that the computer seems to become unresponsive, because the drive keeps saying 'hold on, wait a bit' and with SATA the computer does that. Other type of connections like SAS and NVMe work a bit different so they have that problem a lot less.

A cache drive can solve the issue of having to wait for the drive, but still keep a reasonable speed. With 250mbit you might notice some increase in speed by using a cache, but probably it doesn't matter. With 1gbit you would notice that the drive is really limiting things.

 

If you're going to use a torrent-client inside a VM or docker, you'll want to keep it on a cache or separate drive, but otherwise you won't have issues.

 

 

[kakburken]

3 minutes ago, Wody said:

What I mean is SATA is a great connection, but it isn't very good at doing many things at once. I'm sure you noticed, especially on windows, if you have a list of torrents, and you scroll through them while downloading some, that the computer seems to become unresponsive, because the drive keeps saying 'hold on, wait a bit' and with SATA the computer does that. Other type of connections like SAS and NVMe work a bit different so they have that problem a lot less.

A cache drive can solve the issue of having to wait for the drive, but still keep a reasonable speed. With 250mbit you might notice some increase in speed by using a cache, but probably it doesn't matter. With 1gbit you would notice that the drive is really limiting things.

 

If you're going to use a torrent-client inside a VM or docker, you'll want to keep it on a cache or separate drive, but otherwise you won't have issues.

 

 

Actually i cant recall one single time i had to wait like that. But perhaps my memory is just bad.  But it was A LOT of years since i used HDD's (if that matters in this context with SATA).

 

Anyway.. 

 

Thanks for the clarification!

 

Still unclear why "back in the days", when there wasnt even 100mbit connections, the HDD's (that was already then 7200rpm afaik) had issues when using torrent and downloading (pretty sure it was buffer or some kind of "overload". Memory is fuzzy...) when with the info i've got now from here, seems theres no problem at all downloading torrents to HDD with a 100mbit (or even 250mbit) connection.

 

But i guess i'll notice when i try it out for the first time. I might hold back on the SSD until i atleast tried what happens.

 

My torrent client is inside a docker, but not on the unraid machine. Its located on the Synology NAS. Unraid is just going to be a "share".

 

 

[_cjd_]

Older SATA specs were slower. Heck, 10k rpm SCSI disks were slower. Even now we see incremental improvements in speed across the platter each generation.

[kakburken]

Thanks, didn’t even think about that part. 
that would explain it. I’ll try without cache pool first.

[ConnerVT]

I just broke down why I do not cache my Media share in the post linked below.  You have been given some good advice here.  The only thing I will highlight is you certainly will want at least one solid state drive (NVMe or SSD) to run your applications from.

 

I no longer torrent as I find Usenet a *much* better choice for several reasons.  So how you may best configure transitioning what you seed to what you archive is beyond what I have good advice.

 

 

[kakburken]

9 minutes ago, ConnerVT said:

I just broke down why I do not cache my Media share in the post linked below.  You have been given some good advice here.  The only thing I will highlight is you certainly will want at least one solid state drive (NVMe or SSD) to run your applications from.

 

I no longer torrent as I find Usenet a *much* better choice for several reasons.  So how you may best configure transitioning what you seed to what you archive is beyond what I have good advice.

 

 

Thanks!

 I don’t use Usenet because I’ve got no good nzb's or whatever they’re called. I do have all good torrent trackers though.  so that’s the simple explanation for that.

 

and as i stated a couple of times earlier, this Unraid build will only be storing media. All applications etc will be on another NAS.

 

i see you’re using one share for downloads and one for media (where *arr's have the files moved to). So you’re not using hardlinking since that is considered two different “storage spaces” and hence hardlinking not possible. And by that talking up double the amount of storage for stuff that’s both seeded in download share and stored in media share. If I’m not misunderstanding how you have it setup.

 

The recommendation is to have it all under something like /data. So downloads would be /data/torrent/downloads/ and media would be something like /data/movies/the greatest movie of all time/. that way hardlinking is possible and you save a ton of valuable space (also, the “transfer” to the media folder is almost instantaneously since it’s only linking and not copying files).
 

anyways, it’s a constant battle in my head regarding cache pool.  my guess is that in the end I’ll just buy a m.2 (or two) so I can try both with without cache pool. 

[ConnerVT]

Usenet = Never having to seed.

[kakburken]

6 minutes ago, ConnerVT said:

Usenet = Never having to seed.

Oh ok. Well that seems nice. But if no one is seeding there’s nowhere to download from (I have no idea how usenet works lol)?

 

well doesn’t matter I guess. I’ll never get in to any good nzb's anyway. I think I’m to late to the game. So I need to seed and that means I need it in the same share to be able to hardlink. So in my case I guess I need to use cache on all or nothing.

 

 But I’ll cross that bridge..