From df30f56639f96175ba71d83b4456ccf410c46542 Mon Sep 17 00:00:00 2001 From: Christian Kohlschütter Date: Thu, 16 Jun 2011 21:56:38 +0200 Subject: Add "ashift" property to zpool create Some disks with internal sectors larger than 512 bytes (e.g., 4k) can suffer from bad write performance when ashift is not configured correctly. This is caused by the disk not reporting its actual sector size, but a sector size of 512 bytes. The drive may behave this way for compatibility reasons. For example, the WDC WD20EARS disks are known to exhibit this behavior. When creating a zpool, ZFS takes that wrong sector size and sets the "ashift" property accordingly (to 9: 1<<9=512), whereas it should be set to 12 for 4k sectors (1<<12=4096). This patch allows an adminstrator to manual specify the known correct ashift size at 'zpool create' time. This can significantly improve performance in certain cases. However, it will have an impact on your total pool capacity. See the updated ashift property description in the zpool.8 man page for additional details. Valid values for the ashift property range from 9 to 17 (512B-128KB). Additionally, you may set the ashift to 0 if you wish to auto-detect the sector size based on what the disk reports, this is the default behavior. The most common ashift values are 9 and 12. Example: zpool create -o ashift=12 tank raidz2 sda sdb sdc sdd Closes #280 Original-patch-by: Richard Laager Signed-off-by: Brian Behlendorf --- AUTHORS | 3 +++ 1 file changed, 3 insertions(+) (limited to 'AUTHORS') diff --git a/AUTHORS b/AUTHORS index d7252f5df..d32844c87 100644 --- a/AUTHORS +++ b/AUTHORS @@ -34,3 +34,6 @@ to the project and deserve to be acknowledged. Jim Garlick Manuel Amador (Rudd-O) Gunnar Beutner + Darik Horn + Richard Laager + Christian Kohlschütter -- cgit v1.2.3