[zfs-discuss] Different size / manufacturer L2ARC
I've looked on the mailing list (the evil tuning wikis are down) and haven't seen a reference to this seemingly simple question... I have two OCZ Vertex 4 SSDs acting as L2ARC. I have a spare Crucial SSD (about 1.5 years old) that isn't getting much use and i'm curious about adding it to the pool as a third L2ARC device. Is there any reason why I technically can't use different capacity and/or manufacturer SSDs as a single ZFS pool's L2ARC? Even if it will work technically, will this configuration negatively impact performance (e.g. slow down the entire cache to the slowest drive's performance)? Thanks! Matt ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Different size / manufacturer L2ARC
On 09/26/2012 05:08 PM, Matt Van Mater wrote: I've looked on the mailing list (the evil tuning wikis are down) and haven't seen a reference to this seemingly simple question... I have two OCZ Vertex 4 SSDs acting as L2ARC. I have a spare Crucial SSD (about 1.5 years old) that isn't getting much use and i'm curious about adding it to the pool as a third L2ARC device. Is there any reason why I technically can't use different capacity and/or manufacturer SSDs as a single ZFS pool's L2ARC? No, there isn't. You can do it without problems. Even if it will work technically, will this configuration negatively impact performance (e.g. slow down the entire cache to the slowest drive's performance)? If the added device is slower, you will experience a slight drop in per-op performance, however, if your working set needs another SSD, overall it might improve your throughput (as the cache hit ratio will increase). Cheers, -- Saso ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Different size / manufacturer L2ARC
If the added device is slower, you will experience a slight drop in per-op performance, however, if your working set needs another SSD, overall it might improve your throughput (as the cache hit ratio will increase). Thanks for your fast reply! I think I know the answer to this question, but what is the best way to determine how large my pool's l2arc working set is (i.e. how much l2arc is in use)? Matt ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Different size / manufacturer L2ARC
On 09/26/2012 05:18 PM, Matt Van Mater wrote: If the added device is slower, you will experience a slight drop in per-op performance, however, if your working set needs another SSD, overall it might improve your throughput (as the cache hit ratio will increase). Thanks for your fast reply! I think I know the answer to this question, but what is the best way to determine how large my pool's l2arc working set is (i.e. how much l2arc is in use)? Go grab arcstat.pl from http://blog.harschsystems.com/2010/09/08/arcstat-pl-updated-for-l2arc-statistics/ - that's the tool you're looking for. Cheers, -- Saso ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Different size / manufacturer L2ARC
On 9/26/2012 11:18 AM, Matt Van Mater wrote: If the added device is slower, you will experience a slight drop in per-op performance, however, if your working set needs another SSD, overall it might improve your throughput (as the cache hit ratio will increase). Thanks for your fast reply! I think I know the answer to this question, but what is the best way to determine how large my pool's l2arc working set is (i.e. how much l2arc is in use)? Easiest way: zpool iostat -v ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Different size / manufacturer L2ARC
Excellent thanks to you both. I knew of both those methods and wanted to make sure i wasn't missing something! On Wed, Sep 26, 2012 at 11:21 AM, Dan Swartzendruber dswa...@druber.comwrote: ** On 9/26/2012 11:18 AM, Matt Van Mater wrote: If the added device is slower, you will experience a slight drop in per-op performance, however, if your working set needs another SSD, overall it might improve your throughput (as the cache hit ratio will increase). Thanks for your fast reply! I think I know the answer to this question, but what is the best way to determine how large my pool's l2arc working set is (i.e. how much l2arc is in use)? Easiest way: zpool iostat -v ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
