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is a large ZFS L2ARC relevant when using NFS cache devices?

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is a large ZFS L2ARC relevant when using NFS cache devices?
posted by Doug Atkinson on March 20, 2014, 12:05 p.m. (2 days ago)
Greg

Are you using these ssd's ad read or write devices.   

What type of spinning disk are you using?

Sent from my BlackBerry Z10 smartphone.

Doug

From: greg whynott
Sent: Thursday, March 20, 2014 08:56
To: studiosysadmins-discuss
Reply To: studiosysadmins-discuss@studiosysadmins.com
Subject: [SSA-Discuss] is a large ZFS L2ARC relevant when using NFS cache devices?



Hello,


what are your thoughts on this scenario:


From the perspective of moving data to the clients from the storage solution,  all read,  all NFS v3,  all request hit the Avere units.

A ZFS file server has 2TB of l2arc cache using SL SSD devices and 300 gigs of DRAM cache,   between the file server and HPC there is a cluster of Avere units with 20TB cache.

My thoughts are any objects in the ZFS L2ARC cache would likely already exist on the Avere as they have been requested previously,  therefore any requests the Avere is making back to the storage would be for something which likely is not cached within the ZFS server and would hit the disks directly.

The Avere recycles 6-12 TB of data a day out of its cache for newly requested objects,  and sees an average of 79TB reads from clients.

Would you think 2TB of SSD cache devices in the ZFS server is adding an appreciable amount of performance to the over all storage solution?

We have an opportunity to install the 2TB cache drives in the ZFS solution coming up soon but would rather use them else where if they are not going to bring a lot of win to the table (they cost about $3k each and we would need 5 for each server).  We can't 'try' them without causing a bunch of production drama so that isn't an option,  change control does not allow us to install them into a live system. 


thanks for your time and sharing your opinion on this,
greg

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Greg

Are you using these ssd's ad read or write devices.   

What type of spinning disk are you using?

Sent from my BlackBerry Z10 smartphone.

Doug

From: greg whynott
Sent: Thursday, March 20, 2014 08:56
To: studiosysadmins-discuss
Reply To: studiosysadmins-discuss@studiosysadmins.com
Subject: [SSA-Discuss] is a large ZFS L2ARC relevant when using NFS cache devices?



Hello,


what are your thoughts on this scenario:


From the perspective of moving data to the clients from the storage solution,  all read,  all NFS v3,  all request hit the Avere units.

A ZFS file server has 2TB of l2arc cache using SL SSD devices and 300 gigs of DRAM cache,   between the file server and HPC there is a cluster of Avere units with 20TB cache.

My thoughts are any objects in the ZFS L2ARC cache would likely already exist on the Avere as they have been requested previously,  therefore any requests the Avere is making back to the storage would be for something which likely is not cached within the ZFS server and would hit the disks directly.

The Avere recycles 6-12 TB of data a day out of its cache for newly requested objects,  and sees an average of 79TB reads from clients.

Would you think 2TB of SSD cache devices in the ZFS server is adding an appreciable amount of performance to the over all storage solution?

We have an opportunity to install the 2TB cache drives in the ZFS solution coming up soon but would rather use them else where if they are not going to bring a lot of win to the table (they cost about $3k each and we would need 5 for each server).  We can't 'try' them without causing a bunch of production drama so that isn't an option,  change control does not allow us to install them into a live system. 


thanks for your time and sharing your opinion on this,
greg


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