SSD Cache - no advantage for me?

IF your questions pertains to using the file server performance, transfer issues, jumbo frames tuning, post it here.
Forum rules
We've moved! Head over to Synology Community (community.synology.com) to meet up with our team and other Synology enthusiasts!
dbbarron
Trainee
Trainee
Posts: 12
Joined: Mon Feb 11, 2013 5:38 pm

SSD Cache - no advantage for me?

Unread post by dbbarron » Tue Aug 07, 2018 7:53 pm

I have a SOHO setup DS-918+.
Main daily uses are a Plex server, time machine backup, and security cam recording/management.

I assumed based on my research that these are all essentially streaming uses and an SSD Cache would provide no performance advantage (I'm looking to generally optimize performance, particularly for Plex).

However, the 'SSD Advisor' indicates a recommended 186.2Gb with 14-45Gb/day of total file size and about 1000-5000 files/day.

Hot=23Gb
Warm=162Gb
Cold=647Gb
Archived=4TB.

Is this recommendation appropriate? I suspect this may just show total data accessed rather than how often the same files are accessed which is more accurate for cache prediction.

Can someone please explain.

THX!

pgotze
Experienced
Experienced
Posts: 142
Joined: Thu Oct 03, 2013 8:43 am

Re: SSD Cache - no advantage for me?

Unread post by pgotze » Tue Aug 07, 2018 9:41 pm

I dont think for PLEX usage will be bottleneck in data read from discs. So i guess you will have no real benefit of that.

That you should more or less check in real, to make some real stress tests using your average streaming test scenario and check, if its streaming without issues and if not, check, what is the bottleneck. If you use PLEX seriously, first you should use PLEX subscription and use HW transcoding.
DS918+ (4GB RAM, 2x4TB SHR, 2x256GB read/write cache) business, DS916+(8GB RAM, 3x2TB SHR) home, DS213j(512MB RAM, 1x1 TB single, 1x 500GB single) off-site backup

dbbarron
Trainee
Trainee
Posts: 12
Joined: Mon Feb 11, 2013 5:38 pm

Re: SSD Cache - no advantage for me?

Unread post by dbbarron » Tue Aug 07, 2018 9:47 pm

I should have added that I am using HW transcoding already.

pgotze
Experienced
Experienced
Posts: 142
Joined: Thu Oct 03, 2013 8:43 am

Re: SSD Cache - no advantage for me?

Unread post by pgotze » Wed Aug 08, 2018 2:26 pm

Well then just run streams like you expect in real life on your target devices and check whole chain (NAS CPU - HDD volume - NAS LAN interface - router - wifi or lan of clients). And you will see, where the bottleneck is. You have to really check by your own, there is no generall advice, valid for all in such topic.
DS918+ (4GB RAM, 2x4TB SHR, 2x256GB read/write cache) business, DS916+(8GB RAM, 3x2TB SHR) home, DS213j(512MB RAM, 1x1 TB single, 1x 500GB single) off-site backup

itsjasper
Beginner
Beginner
Posts: 20
Joined: Tue Nov 17, 2015 12:25 pm

Re: SSD Cache - no advantage for me?

Unread post by itsjasper » Thu Aug 09, 2018 12:36 am

You’ll definitely see an improvement in the Plex web front end, things like the movies and tv shows artwork and internal databases will get cached.

mervincm
Knowledgeable
Knowledgeable
Posts: 341
Joined: Wed Jul 30, 2014 6:08 am

Re: SSD Cache - no advantage for me?

Unread post by mervincm » Thu Aug 09, 2018 2:06 am

itsjasper wrote:
Thu Aug 09, 2018 12:36 am
You’ll definitely see an improvement in the Plex web front end, things like the movies and tv shows artwork and internal databases will get cached.
This is what I was going to say. I have my plex server installed on an SSD volume now, and it is much snappier than it used to be. My Plex Library folder is only 50GB but it has 260,000 files. loading up all that metadata to construct the client experience is much faster from SSD than from HDD. SSD volume works better for me than SSD cache did, but it you don't have the slots to spare, I would definitely try SSD cache.
1815+ (factory patched board) 4GB 5x6TB WD RED

Squozen
Guru
Guru
Posts: 1561
Joined: Wed Jan 09, 2013 1:35 am

Re: SSD Cache - no advantage for me?

Unread post by Squozen » Thu Aug 09, 2018 10:10 am

I think a cache is a waste of money after having tried it and would recommend adding more RAM to the NAS instead.

User avatar
-Robbie-
Beginner
Beginner
Posts: 28
Joined: Sat Aug 26, 2017 9:49 pm
Location: UK

Re: SSD Cache - no advantage for me?

Unread post by -Robbie- » Wed Sep 05, 2018 7:52 am

Plex and Time Machine user here with assorted other files archived or used as live data. SSD cache made a dramatic change in performance for me and after running with an SSD in a bay running as a read-only cache I have recently moved to a RAID 1 read/write cache in the PCIe slot.

With the cache Plex is noticeably snappier, especially with more than 1 client and has given the CPU a little more headroom too. Clearly no difference in playing a movie but the cache is also active when recording multiple TV broadcasts (HDHomeRun).

Arguably the biggest change was for TM backups. There are a surprising amount of reads during a TM backup and the cache is used extensively. With 6 Time Machine clients doing their thing every hour this has given the NAS quite a speed boost.

I only have 1 NAS so it gets used for everything from media, databases, backups, remote servers, DNS, Plex et al - so quite a mixed workload for the cache. With 16GB of memory I also make full use of RAM cache too.

The SSD cache advisor is helpful and in my case my actual cache size is larger than the advisor suggested. I have about 60GB of 'hot' data and around 70GB of 'warm'.

I am considering using a bay for a pure SSD 'performance' volume, primarily for Plex, as that also seems like a potentially significant boost for the system.
Synology DS1517+ | 16GB | SHR/Btrfs | 2-port ALB | 2 x 3TB + 2 x 4TB WD Red & 1 x 1TB 860 Evo SSD | 2 x 256GB 860 Evo M.2 SSD | M2D18 PCIe
Supported by: EdgeRouter 8 | EdgeSwitch 24 |

Locked

Return to “File Server Performance”