Register for the iXsystems Community to get an ad-free experience and exclusive discounts in our eBay Store.

My Journey into the world of FreeNas (includes pictures of build)

Chris Moore

Super Moderator
Moderator
Joined
May 2, 2015
Messages
9,111
Thanks
2,871
#21
Not sure what I'm going todo with all this ram... maybe offer it up to anyone that can make use of it
I would volunteer to have some of the memory. Probably would cost too much to ship though.
 

pro lamer

FreeNAS Guru
Joined
Feb 16, 2018
Messages
594
Thanks
104
#22
A SLOG can only ever slow down your NAS
Yes. But it is faster 100% of the time to disable sync writes.
I'm trying to understand this part of the conversation properly, too: can it be summarized: the OP is not using sync writes so when he/she started using sync writes and a SLOG the performance would drop because of the sync writes despite the SLOG... ( ? ) And sync writes without a SLOG would be terrible in terms of performance but sync writes with a SLOG would still be slower than non-sync writes without the SLOG in this case?

Sent from my phone
 
Joined
Oct 18, 2018
Messages
248
Thanks
138
#23
Someone feel free to correct me if I am wrong.

[if] the OP is not using sync writes [so] when he/she started using sync writes and a SLOG the performance would drop because of the sync writes despite the SLOG...
I think this is spot on.

And sync writes without a SLOG would be terrible in terms of performance but sync writes with a SLOG would still be slower than non-sync writes without the SLOG in this case?
Yes, I believe this is true as well.

I suspect that the informative speed comparisons are sync vs async writes and SLOG vs no SLOG. Comparing sync writes with SLOG vs async writes of any kind seems to only be informative of sync vs async writes and not really about the SLOG. This is because of the extremely different ways in which sync and async writes behave.

I think a relevant takeaway is that if you're going to use sync writes with a SLOG you should use an appropriate SLOG, such as a one with PLP. If you do not, you might as well use async writes since using a SLOG without PLP defeats much of the purpose of sync writes. To quote from jreco
My point with you was that your SLOG device isn't providing the guarantee that a SLOG is supposed to - which is that sync writes are committed.
With reasonable workflows I think one would expect async writes with SLOG|without SLOG to be the fastest, followed by sync writes with an appropriate SLOG, followed by sync writes where the ZIL lives in the pool.
 

jgreco

Resident Grinch
Moderator
Joined
May 29, 2011
Messages
11,597
Thanks
2,896
#24
This is because of the extremely different ways in which sync and async writes behave.
That might be the wrong way to think about it.

Writes to the pool are *always* handled through the pool transaction group mechanism and this represents the maximum possible performance for the system. This also happens to be the exact data flow for async writes.

Sync writes do exactly the same thing, except that before the write returns success to the user, it *also* calls an additional function to commit the transaction to the ZIL/SLOG.

To my way of thinking, that means "extremely different ways" is a poor way to describe it, because functionally they are extremely similar, except that sync writes add one more step, one that requires a complete traversal of all the steps needed to commit the data to storage, which is generally a slow-ish operation.

The one more step is always going to take more time. The poster was talking about having an SSD without power loss protection acting as a SLOG, which doesn't have the correct characteristics to act as a SLOG. Therefore the best course of action would be just to ditch that, and gain back the unnecessary loss of speed. Ditching the additional step is *always* faster.
 
Joined
Mar 30, 2019
Messages
14
Thanks
5
#25
That might be the wrong way to think about it.
The poster was talking about having an SSD without power loss protection acting as a SLOG, which doesn't have the correct characteristics to act as a SLOG. Therefore the best course of action would be just to ditch that, and gain back the unnecessary loss of speed. Ditching the additional step is *always* faster.
What I've learnt from this conversation and linked posts is that actually, no slog at all and "sync writes off" is the fastest way to write data, although the trade-off is "risk to data in power loss scenario", and that if I want the full protection that ZFS can offer, then I need a slog that has the ability to protect against power lose....

I have seen a lot of people praising optane, and although the ARK page on intel's site state they don't have PLP, because they write directly to storage (no DRAM buffer ech), that these can make good SLOG drives?

The problem I have is justifying the cost of a 280Gb PCIe optane drive as a Slog knowing that probably less than 10Gb will ever be used at any one time... (I know it'll aid wear levelling as its not actually the same 10Gb that gets used over and over) So i'm not researching the metrics of partitioning it up for use as a SLOG and L2ARC...

the learning curve continues :)
 
Joined
Jan 6, 2016
Messages
22
Thanks
5
#26
@Sprint First of all, congrats for your very nice build.

Can you please tell me what is this?

1558206156328.png



I plan to build a system with up to 3 HBA's and other things. I usually use some cheap / low noise 40 mm fans for H200 / H310 HBA's. If i keep them i can't put them near, will not fit.
So i ordered https://www.amazon.co.uk/gp/product/B079NJVGXS/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1]this[/url] and https://www.amazon.co.uk/gp/product/B07H32NFX1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1]this[/url].
I think your solution si better. :) It's plastic, aluminium or other material!?
Did you find also narow ILM on your Artic coolers or just the square ones?

Thank you!
 
Joined
Mar 30, 2019
Messages
14
Thanks
5
#27
@Sprint

Can you please tell me what is this?
Its actually a radiator bracket (steal i think) i had spare from installing my water cooled graphics card in my PC.... So its abit of a bodge.... the tape on the end is just to ensure it doesn't short against anything.

https://www.overclockers.co.uk/bitspower-120-radiator-holder-wc-337-bp.html

Your Artic coolers have the narow ILM also in the pachage?

Thank you!
Mine are sqaure, not sure if they'd fit with narrow... these are them for reference

https://www.amazon.co.uk/gp/product/B06WV898Y1/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
 
Joined
Mar 30, 2019
Messages
14
Thanks
5
#28
In other news... the migration of data off of my Synology box has been completed, so the 6 reds could come out and be added to two more white label (but in essence the same reds) and be added into my chassis in Raid2Z! Threw in a 240Gb Sandisk SSD as a L2ARC for good measure.
InkedIMG_2338_LI.jpg
 

Snow

FreeNAS Experienced
Joined
Aug 1, 2014
Messages
217
Thanks
56
#29
Dam sexy Pic!!!
 
Last edited:

pro lamer

FreeNAS Guru
Joined
Feb 16, 2018
Messages
594
Thanks
104
#30
Top