Bug#593658: default compression=on?
Starting with jessie, newly-created zpools have the lz4_compress feature enabled. Their metadata will be always compressed with LZ4. But compression of file *data* is still disabled by default (compression=off option). lz4 is so fast, and the overhead so small that it probably makes performance sense to enabled it, whether you think your data will be compressable or not, But I agree with Witold's comments[0] that compression has some unexpected effects in userland. (Some Debian package testsuites will actually fail). It perhaps should not be enabled by default just yet, but we should try to make it install-time selectable within d-i: [0]: https://bugs.debian.org/593658#32 Regards, -- Steven Chamberlain ste...@pyro.eu.org -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Bug#593658: default compression=on?
Please do not change default of compression. I have compression enabled on most of my datasets, but it really should not be default. This can break existings assumptions and scripts (for example from solaris or freebsd). Much better would be change debian-installer to create dataset with compression as an option. Also things like copies=2 can be added to debian-installer, as it can be very usefull for system data, especially if we are installing on single disk (i.e. laptop). But nobody is suggesting makeing copies=2 a default for zfs create. If people will want to enable compression they will enabled it, when they find it beneficial. If there are anyone making compression=on a default, i would only think as upstream to make this decision after extremly extensive testing as it needs lots of knowledge to state that it do not introduce considerable regressions. Just my $.02 -- Witold Baryluk signature.asc Description: Digital signature
Bug#593658: default compression=on?
Brett Dikeman a écrit : On Thu, Aug 19, 2010 at 8:55 PM, Tuco tuco@gmail.com wrote: I suggest enabling compression by default when creating new ZFS filesystems. I suggest giving the user the option during an install, if ZFS is supported in that phase. That has a definite benefit, as ZFS only compresses data that makes it to disk after compression is flipped on. Turning on compression after an install is, at least for things like /usr, largely pointless; eventually, as packages get updated etc, more and more of the filesystem will become compressed, but... Point worth noting: it's only of value if the data you have is by and large compressable! If you're a photographer and work with mostly RAW and JPEGs, compression is going to be a waste of CPU cycles and maybe (this is a wild guess) increase CPU cache misses? It'd probably be worth talking to the ZFS developers to find out why compression isn't enabled by default in Solaris/OpenSolaris. They probably had some logic behind it, and it might be relevant. I agree that enabling it by default without understanding all the benefits/drawback is not something that should be done. Especially if the default is different that what user expect (it is not the default on OpenSolaris/FreeBSD, btrfs compression is disabled by default). The best would indeed be to provide a way to create ZFS partitions during the installation. Currently this is not the case, and there is some work to do here. It is probably not straightforward, as you first need to create a pool, then a filesystem. It's probably comparable to an LVM installation in some senses. If someone wants to start working on partman-zfs, please note that the zfsutils-udeb is available, and that a patch for parted has been posted on the parted-devel mailing-list. -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurel...@aurel32.net http://www.aurel32.net -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Bug#593658: default compression=on?
On Thu, Aug 19, 2010 at 09:30:33PM -0400, Brett Dikeman scribbled: On Thu, Aug 19, 2010 at 8:55 PM, Tuco tuco@gmail.com wrote: I suggest enabling compression by default when creating new ZFS filesystems. I suggest giving the user the option during an install, if ZFS is I suggest running more benchmarks before suggesting the default should be changed. :) The benchmark in question was measuring the time and energy used while copying a file already on the same filesystem, on some unspecified laptop. Do we really want to optimize for copying files on an otherwise idle computer with a slow disk while completely ignoring any effects this might have on desktops, servers, or computers that are actually doing something? BTW, I expect deduplication would have a much more drastic effect on this benchmark. We should turn it on by default. /s It'd probably be worth talking to the ZFS developers to find out why compression isn't enabled by default in Solaris/OpenSolaris. They probably had some logic behind it, and it might be relevant. My guess would be that they are optimizing for computers that actually compute things. Another reason might be that if the filesystem explodes it is easier to recover uncompressed files, although I get the feeling ZFS developers like to think that would never be necessary. But, yeah, it's probably worth checking with them before changing the default. Ivan -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
Bug#593658: default compression=on?
Package: zfsutils Version: 8.1-3 Tags: patch Compression in ZFS has a triple benefit in IO performance, disk space and energy consumption, this article explains (with benchmarks): http://blogs.sun.com/partnertech/entry/zfs_compression_perf_disk_space IO improvement isn't obvious: reading and writing takes less time when compressing or decompressing because CPU is not the bottleneck. The linked article explains in more detail. I suggest enabling compression by default when creating new ZFS filesystems. --- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h 2010-05-24 06:09:36.0 -0400 +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h 2010-08-19 18:52:33.995673472 -0400 @@ -98,7 +98,7 @@ }; #define ZIO_COMPRESS_ON_VALUE ZIO_COMPRESS_LZJB -#define ZIO_COMPRESS_DEFAULT ZIO_COMPRESS_OFF +#define ZIO_COMPRESS_DEFAULT ZIO_COMPRESS_ON #define ZIO_FAILURE_MODE_WAIT 0 #define ZIO_FAILURE_MODE_CONTINUE 1
Bug#593658: default compression=on?
On Thu, Aug 19, 2010 at 8:55 PM, Tuco tuco@gmail.com wrote: I suggest enabling compression by default when creating new ZFS filesystems. I suggest giving the user the option during an install, if ZFS is supported in that phase. That has a definite benefit, as ZFS only compresses data that makes it to disk after compression is flipped on. Turning on compression after an install is, at least for things like /usr, largely pointless; eventually, as packages get updated etc, more and more of the filesystem will become compressed, but... Point worth noting: it's only of value if the data you have is by and large compressable! If you're a photographer and work with mostly RAW and JPEGs, compression is going to be a waste of CPU cycles and maybe (this is a wild guess) increase CPU cache misses? It'd probably be worth talking to the ZFS developers to find out why compression isn't enabled by default in Solaris/OpenSolaris. They probably had some logic behind it, and it might be relevant. -B -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org
