Large SAN, Supermicro Hardware, SSDs - Setup Ideas

[dddza]

Hello Everybody :)

Having previously used Nexenta, I'm now playing with FreeNAS and already loving it. I am trying to understand the ideal setup using the hardware that we have, especially that of SSD drives for LOG and CACHE drives - if it's a great addition or even required.

Hardware Setup:

Chassis: SC936E26-R1200B - Supermicro 16 Bay
Board: Supermicro X9SCM-F
CPU: Intel Xeon E3-1220 Sandy Bridge
RAM: 4 x 4GB (16GB)
Drives: 16 x Seagate SV35 - 2TB

FreeNAS to be installed on mini Sony 16GB USB device plugged directly onto the board.

I'll be using a mix of iSCSI and NFS for storage. ZFS with 2-3 parity drives.

SSDs: 3 x Intel 320 Series 40GBs

In the past with Nexenta I have used a 80GB SSD for LOG and 120GB for CACHE drives. I'm not so sure on the advantages of this, or to even have these running on different drives. This originally came under recommendation of somebody who pretty much said "just do it this way", with little explanation as to why.

I've searched around and tried reading up but don't find much related to exactly what I'm wanting to do or using the above spec, with SSDs and so forth. Perhaps it's not even required?

I just need some pointers in the right direction here with some brief assistance.

Any comments/feedback or further reading would be greatly appreciated.

Thank you in advance :)

 

[peterh]

As you cannot remove or even continue to run with a failaing LOG device in zfs version 15
i'd recommend that you start without one. It's only contributing where violent writing anyway.

See freebsd handbook for zfs discussion
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/

 

[dddza]

As you cannot remove or even continue to run with a failaing LOG device in zfs version 15
i'd recommend that you start without one. It's only contributing where violent writing anyway.

See freebsd handbook for zfs discussion
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/

Oh wow.. thank you for this! Very interesting.

What about as a cache drive?

 

[paleoN]

Oh wow.. thank you for this! Very interesting.

What about as a cache drive?

Read through this [thread=7189]thread[/thread] over on the hardware forum.

Can't say I'm a fan of your SV35s for a NAS.

What type of pool or pools are you planning?

 

[dddza]

Can't say I'm a fan of your SV35s for a NAS.

Any reason why? Am really keen to know.

What type of pool or pools are you planning?

Will find out, not entirely sure.

Am on my way to the link for a read.

 

[peterh]

About log and cache devices , a good starting poing might be :
http://constantin.glez.de/blog/2011/02/frequently-asked-questions-about-flash-memory-ssds-and-zfs

a freebsd 'tinted' tread is :
http://forums.freebsd.org/showthread.php?t=20873

 

[dddza]

About log and cache devices , a good starting poing might be :
http://constantin.glez.de/blog/2011/02/frequently-asked-questions-about-flash-memory-ssds-and-zfs

a freebsd 'tinted' tread is :
http://forums.freebsd.org/showthread.php?t=20873

Fantastic!! Thank you for this, am reading over it already.

 

[louisk]

As you cannot remove or even continue to run with a failaing LOG device in zfs version 15
i'd recommend that you start without one. It's only contributing where violent writing anyway.

See freebsd handbook for zfs discussion
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/

If memory serves, when you attempt to assign a single device to the ZIL, it mentions that and you have an opportunity to create a mirrored device to use for the ZIL.

 

[louisk]

Hello Everybody :)
...
In the past with Nexenta I have used a 80GB SSD for LOG and 120GB for CACHE drives. I'm not so sure on the advantages of this, or to even have these running on different drives. This originally came under recommendation of somebody who pretty much said "just do it this way", with little explanation as to why.

I've searched around and tried reading up but don't find much related to exactly what I'm wanting to do or using the above spec, with SSDs and so forth. Perhaps it's not even required?
...

ZFS tries to cache information in RAM so its faster to retrieve. This is why it has high memory requirements, and also why you put as much memory in it as you can. L2ARC (cache) drives are used to augment this. SSD is slower than RAM, but still faster than going out to disk for data.

The ZIL is not needed until you're pushing at least 800MB/s (bytes with a big B). SSD/RAM drive for ZIL gets you from 1Gb/s to 10Gb/s.

 

[paleoN]

Can't say I'm a fan of your SV35s for a NAS.

Any reason why? Am really keen to know.

And back to the hard drives... Do not use a video hard drive for a computer. Video hard drives allow for errors and just skip right through the data in favor of keeping the video running. Odds are the person watching TV will never notice the dozens of read errors while watching a recorded program. BUT an computer will crash, it can't handle bad data so well. Video drives are great for a TiVo or DVR and I use them myself in that capacity.

Which I have seen elsewhere on the web as well.

 

[dddza]

Thank you so much for the replies thus far - will continue my research :)