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问题
我最近安装了一个新磁盘并在其上创建了一个zpool： /# zpool create morez /dev/sdb
使用它一段时间后,我注意到它很慢： /morez# fio --name rw --rw rw --size 10G read: IOPS=19.6k, BW=76.6MiB/s (80.3MB/s)(5120MiB/66834msec) write: IOPS=19.6k, BW=76.6MiB/s (80.3MB/s)(5120MiB/66834msec) 此测试与我的实际用例非常相似.我正在从磁盘读取中等数量(~10k)的图像(每个~2 MiB).当磁盘大部分为空时,它们都被立即写入,因此我不认为它们会被分割. 为了比较,我测试了ext4： /# gdisk /dev/sdb ... /# mkfs.ext4 -f /dev/sdb1 && mount /dev/sdb1 /mnt && cd /mnt /mnt# fio --name rw --rw rw --size 10G read: IOPS=48.3k, BW=189MiB/s (198MB/s)(5120MiB/27135msec) write: IOPS=48.3k, BW=189MiB/s (198MB/s)(5120MiB/27135msec) 和btrfs： /# mkfs.btrfs -f /dev/sdb1 && mount /dev/sdb1 /mnt && cd /mnt /mnt# fio --name rw --rw rw --size 10G read: IOPS=51.3k, BW=201MiB/s (210MB/s)(5120MiB/25528msec) write: IOPS=51.3k, BW=201MiB/s (210MB/s)(5120MiB/25528msec) 可能导致ZFS性能问题的原因是什么？如何让它更快？ 尝试解决方案失败 我还尝试显式设置zpool的扇区大小,因为我的磁盘(Seagate ST1000DM003)使用4096字节的物理扇区： /# zpool create -o ashift=12 morez /dev/sdb
这没有改善性能： /morez# fio --name rw --rw rw --size 10G read: IOPS=21.3k, BW=83.2MiB/s (87.2MB/s)(5120MiB/61573msec) write: IOPS=21.3k, BW=83.2MiB/s (87.2MB/s)(5120MiB/61573msec) 意见 奇怪的是,使用zvol有很好的表现： /# zfs create -V 20G morez/vol /# fio --name rw --filename /dev/zvol/morez/vol --rw rw --size 10G read: IOPS=52.7k, BW=206MiB/s (216MB/s)(5120MiB/24852msec) write: IOPS=52.7k, BW=206MiB/s (216MB/s)(5120MiB/24852msec) 为什么这只影响ZFS文件系统而不影响zvols？ btrfs的扩展测试 在评论中,有人认为差异可能是由于缓存造成的.经过进一步测试,我不相信是这种情况.我将btrfs测试的大小增加到远高于我的计算机的内存量,其性能仍远远高于ZFS： /# mkfs.btrfs -f /dev/sdb1 && mount /dev/sdb1 /mnt && cd /mnt /mnt# $fio --name rw --rw rw --size 500G --runtime 3600 --time_based --ramp_time 900 read: IOPS=41.9k, BW=164MiB/s (172MB/s)(576GiB/3600003msec) write: IOPS=41.9k, BW=164MiB/s (172MB/s)(576GiB/3600003msec) 系统信息 软件 > Arch Linux,内核版本4.11.6 硬件 >正在测试的驱动器：Seagate ST1000DM003,连接到6Gb / s SATA端口 ZFS信息 以下是运行fio之前ZFS属性的样子.这些只是使用默认设置创建zpool的结果. # zpool get all morez NAME PROPERTY VALUE SOURCE morez size 928G - morez capacity 0% - morez altroot - default morez health ONLINE - morez guid [removed] default morez version - default morez bootfs - default morez delegation on default morez autoreplace off default morez cachefile - default morez failmode wait default morez listsnapshots off default morez autoexpand off default morez dedupditto 0 default morez dedupratio 1.00x - morez free 928G - morez allocated 276K - morez readonly off - morez ashift 0 default morez comment - default morez expandsize - - morez freeing 0 default morez fragmentation 0% - morez leaked 0 default morez feature@async_destroy enabled local morez feature@empty_bpobj enabled local morez feature@lz4_compress active local morez feature@spacemap_histogram active local morez feature@enabled_txg active local morez feature@hole_birth active local morez feature@extensible_dataset enabled local morez feature@embedded_data active local morez feature@bookmarks enabled local morez feature@filesystem_limits enabled local morez feature@large_blocks enabled local # zfs get all morez NAME PROPERTY VALUE SOURCE morez type filesystem - morez creation Thu Jun 29 19:34 2017 - morez used 240K - morez available 899G - morez referenced 96K - morez compressratio 1.00x - morez mounted yes - morez quota none default morez reservation none default morez recordsize 128K default morez mountpoint /morez default morez sharenfs off default morez checksum on default morez compression off default morez atime on default morez devices on default morez exec on default morez setuid on default morez readonly off default morez zoned off default morez snapdir hidden default morez aclinherit restricted default morez canmount on default morez xattr on default morez copies 1 default morez version 5 - morez utf8only off - morez normalization none - morez casesensitivity sensitive - morez vscan off default morez nbmand off default morez sharesmb off default morez refquota none default morez refreservation none default morez primarycache all default morez secondarycache all default morez usedbysnapshots 0 - morez usedbydataset 96K - morez usedbychildren 144K - morez usedbyrefreservation 0 - morez logbias latency default morez dedup off default morez mlslabel none default morez sync standard default morez refcompressratio 1.00x - morez written 96K - morez logicalused 72.5K - morez logicalreferenced 40K - morez filesystem_limit none default morez snapshot_limit none default morez filesystem_count none default morez snapshot_count none default morez snapdev hidden default morez acltype off default morez context none default morez fscontext none default morez defcontext none default morez rootcontext none default morez relatime off default morez redundant_metadata all default morez overlay off default |
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