Un disque de 'cache' ?

[playzir]

Bonjour,
J'ai entendu parlé que l'on pouvait ajouter 1 ou 2 disques de 'cache', ce qui permettrait d'améliorer considérablement les performances de transferts.
Mais je ne maitrise pas tout, serait-il possible de m'expliquer les bases de cette fonction ? Et si cela a un réel impact sur la vitesse de transfert ?
Comment mettre en place ce système sur truenas ?
Je vous remercie par avance

 

[Pitfrr]

Bonjour,

Un disque de cache devient intéressant lorsque l'on a maximisé la RAM (et plutôt vers les 128Go que 16Go).
Je n'ai pas d'expérience avec les disques de cache et pour une utilisation domestique mais ma compréhension du cache pour TrueNAS est la suivante (encore une fois, je n'en utilise pas donc je ne suis pas très versé sur le sujet):

On peut mettre en place deux types de cache: L2ARC et SLOG (note que pour le SLOG c'est un peu un abus de langage de parler de cache...).

• Le L2ARC va venir compléter le cache ARC (en RAM). Donc il faut regarder au niveau du système si ce dernier sature déjà au niveau du ARC. Si c'est le cas, rajouter un cache L2ARC ne va pas forcément aider non plus, cela dépend de la situation (on va d'abord augmenter la RAM au maximum).
• Le SLOG va mettre en cache des méta données du volume (et va aider principalement pour des écritures synchrones). Par contre, il faut pas prendre n'importe quoi comme périphérique, sinon l'effet sera à l'opposé des attentes.

Bref pour faire simple: non je ne pense pas que tu aies besoin de cela...

 

[Ashka]

Bonjour,

je m’intéresse a ce poste car je me posait la même question aussi, j'ai 96Go de RAM et souvent le ZFS cache bouffe toute la RAM
du coup ce L2ARC serait il utile ?? et peu ton attribuer ce Cache a 2 pool en même temps ou c'est un disque Nvme par pool ?
Merci.

 

[Pitfrr]

le ZFS cache bouffe toute la RAM

Ca c'est normal... Le cache ARC va prendre toute la RAM qu'il peut mais ça ne veut pas dire que tu as intérêt à mettre un L2ARC.
Pour cela il faut regarder au niveau des statistiques sur les requêtes ARC, c'est ce qui te donnera un peu plus d'information sur l'utilité d'un cache ou pas.

 

[alexgamer06]

Bonjour, on voit cela ou les statistiques des requêtes arc ?

 

[sretalla]

arc_summary

 

[alexgamer06]

arc_summary

Merci

 

[jgreco]

*Carte Adaptec Raid ASR-6805T 512Mo 8 Ports.

What's all the noise about HBAs, and why can't I use a RAID controller?

1) An HBA is a Host Bus Adapter. This is a controller that allows SAS and SATA devices to be attached to, and communicate directly with, a server. RAID controllers typically aggregate several disks into a Virtual Disk abstraction of some sort...

www.truenas.com

 

[Ashka]

*Carte Adaptec Raid ASR-6805T 512Mo 8 Ports.

What's all the noise about HBAs, and why can't I use a RAID controller?

1) An HBA is a Host Bus Adapter. This is a controller that allows SAS and SATA devices to be attached to, and communicate directly with, a server. RAID controllers typically aggregate several disks into a Virtual Disk abstraction of some sort...

www.truenas.com

My Raid card works perfectly ;)

 

[jgreco]

My Raid card works perfectly ;)

Yup. That's the way it seems, until one day you end up with a corrupt pool, complain about it here, and then that mean Grinch guy quips "So I see".

It's happened before, and attitudes like yours ensure it will happen again. Good luck.

 

[Ashka]

Yup. That's the way it seems, until one day you end up with a corrupt pool, complain about it here, and then that mean Grinch guy quips "So I see".

It's happened before, and attitudes like yours ensure it will happen again. Good luck.

thanks but its ok for me, with the RAID card i have created one volume by disk, not a raid array, i created raid array on Truenas.
but i will take your advise, what do you advise me ? what HBA card ? thank you.

ps: is this card ok ? : https://www.ebay.fr/itm/12269947942...D%3D|ampid:PL_CLK|clp:2047675&epid=1150963694

 

[jgreco]

thanks but its ok for me, with the RAID card i have created one volume by disk, not a raid array, i created raid array on Truenas.
but i will take your advise, what do you advise me ? what HBA card ? thank you.

ps: is this card ok ? : https://www.ebay.fr/itm/12269947942...D%3D|ampid:PL_CLK|clp:2047675&epid=1150963694

Yes, that model of card is perfectly fine. However, be aware that many cards from China may be fake.

Hardware Buying Guide - some tips for not getting ripped off

This resource was originally created by user: jgreco on the TrueNAS Community Forums Archive. Please DM this account or comment in this thread to claim it. I’ve been giving this information out piecemeal for years, and should maybe have it summarized in one place. There’s been a lot of people...

www.truenas.com

 

[Ashka]

Yes, that model of card is perfectly fine. However, be aware that many cards from China may be fake.

Hardware Buying Guide - some tips for not getting ripped off

This resource was originally created by user: jgreco on the TrueNAS Community Forums Archive. Please DM this account or comment in this thread to claim it. I’ve been giving this information out piecemeal for years, and should maybe have it summarized in one place. There’s been a lot of people...

www.truenas.com

ok thank you i will buy two of them.
You know how we can know if its fake or not ?
is there a special firmware for this card ?P20 IT mode i don't know what..

 

[jgreco]

You want the firmware 20.00.07.00 which is available as an attachment on many of the web pages that describe how to crossflash to IT mode. I believe Stilez has a resource in the Resources section that has this.

Knowing whether a card is fake or not is difficult. They can be pretty good and have gotten better over the years. I've made some notes and also a link to a video dedicated to the topic over here.

Fake server cards

This resource was originally created by user: jgreco on the TrueNAS Community Forums Archive. Please DM this account or comment in this thread to claim it. Some time ago, forum frequenter @artlessknave kindly sent me a pair of LSI HBA cards that had failed to work out in a FreeNAS build. Having...

www.truenas.com

 

[Ashka]

You want the firmware 20.00.07.00 which is available as an attachment on many of the web pages that describe how to crossflash to IT mode. I believe Stilez has a resource in the Resources section that has this.

Knowing whether a card is fake or not is difficult. They can be pretty good and have gotten better over the years. I've made some notes and also a link to a video dedicated to the topic over here.

Fake server cards

This resource was originally created by user: jgreco on the TrueNAS Community Forums Archive. Please DM this account or comment in this thread to claim it. Some time ago, forum frequenter @artlessknave kindly sent me a pair of LSI HBA cards that had failed to work out in a FreeNAS build. Having...

www.truenas.com

ok thank you for the video, its very interessant, but its true, its difficult to see the difference between both cards..
but i think i will buy two of this : https://www.ebay.fr/itm/125553361907

you think is a good choice ?

 

[jgreco]

If it's a legit card, it will work. If it's a fake card, it still might work. If it doesn't work, ask eBay for your money back.

 

[Ashka]

If it's a legit card, it will work. If it's a fake card, it still might work. If it doesn't work, ask eBay for your money back.

ok thank you for your help :)

PS: Can i use 12Gbs SAS drive on this 6GBs LSi card ??