Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-11 Thread Jim Klimov
2012-01-11 1:26, Jim Klimov пишет: To follow on the subject of VDEV caching, even if only of metadata, in oi_148a, I have found the disabling entry in /etc/system of the LiveUSB: set zfs:zfs_vdev_cache_size=0 Now that I have the cache turned on and my scrub continues, cache efficiency so far

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-10 Thread Jim Klimov
To follow on the subject of VDEV caching, even if only of metadata, in oi_148a, I have found the disabling entry in /etc/system of the LiveUSB: set zfs:zfs_vdev_cache_size=0 Now that I have the cache turned on and my scrub continues, cache efficiency so far happens to be 75%. Not bad for a

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-09 Thread John Martin
On 01/08/12 20:10, Jim Klimov wrote: Is it true or false that: ZFS might skip the cache and go to disks for streaming reads? I don't believe this was ever suggested. Instead, if data is not already in the file system cache and a large read is made from disk should the file system put this

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-09 Thread Jim Klimov
Thanks for the replies, some more questions follow. Your answers below seem to contradict each other somewhat. Is it true that: 1) VDEV cache before b70 used to contain a full copy of prefetched disk contents, 2) VDEV cache since b70 analyzes the prefetched sectors and only keeps metadata

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-09 Thread John Martin
On 01/08/12 10:15, John Martin wrote: I believe Joerg Moellenkamp published a discussion several years ago on how L1ARC attempt to deal with the pollution of the cache by large streaming reads, but I don't have a bookmark handy (nor the knowledge of whether the behavior is still accurate).

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-09 Thread Jim Klimov
2012-01-09 18:15, John Martin пишет: On 01/08/12 20:10, Jim Klimov wrote: Is it true or false that: ZFS might skip the cache and go to disks for streaming reads? (The more I think about it, the more senseless this sentence seems, and I might have just mistaken it with ZIL writes of bulk

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Edward Ned Harvey
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- boun...@opensolaris.org] On Behalf Of Jim Klimov I wonder if it is possible (currently or in the future as an RFE) to tell ZFS to automatically read-ahead some files and cache them in RAM and/or L2ARC? One use-case would be

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread John Martin
On 01/08/12 09:30, Edward Ned Harvey wrote: In the case of your MP3 collection... Probably the only thing you can do is to write a script which will simply go read all the files you predict will be read soon. The key here is the prediction - There's no way ZFS or solaris, or any other OS in

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Jim Klimov
2012-01-08 19:15, John Martin пишет: On 01/08/12 09:30, Edward Ned Harvey wrote: In the case of your MP3 collection... Probably the only thing you can do is to write a script which will simply go read all the files you predict will be read soon. The key here is the prediction - There's no way

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread John Martin
On 01/08/12 11:30, Jim Klimov wrote: However for smaller servers, such as home NASes which have about one user overall, pre-reading and caching files even for a single use might be an objective per se - just to let the hard-disks spin down. Say, if I sit down to watch a movie from my NAS, it is

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Jim Klimov
2012-01-09 0:29, John Martin пишет: On 01/08/12 11:30, Jim Klimov wrote: However for smaller servers, such as home NASes which have about one user overall, pre-reading and caching files even for a single use might be an objective per se - just to let the hard-disks spin down. Say, if I sit

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Richard Elling
On Jan 7, 2012, at 8:59 AM, Jim Klimov wrote: I wonder if it is possible (currently or in the future as an RFE) to tell ZFS to automatically read-ahead some files and cache them in RAM and/or L2ARC? See discussions on the ZFS intelligent prefetch algorithm. I think Ben Rockwood's description

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Jim Klimov
2012-01-09 4:14, Richard Elling пишет: On Jan 7, 2012, at 8:59 AM, Jim Klimov wrote: I wonder if it is possible (currently or in the future as an RFE) to tell ZFS to automatically read-ahead some files and cache them in RAM and/or L2ARC? See discussions on the ZFS intelligent prefetch

Re: [zfs-discuss] zfs read-ahead and L2ARC

2012-01-08 Thread Richard Elling
On Jan 8, 2012, at 5:10 PM, Jim Klimov wrote: 2012-01-09 4:14, Richard Elling пишет: On Jan 7, 2012, at 8:59 AM, Jim Klimov wrote: I wonder if it is possible (currently or in the future as an RFE) to tell ZFS to automatically read-ahead some files and cache them in RAM and/or L2ARC? See