From 143c7cf8e9331dc1ed2c86d9d6c46ff55f5fde3e Mon Sep 17 00:00:00 2001 From: Rajeev Mishra Date: Thu, 22 Aug 2024 18:04:26 +0000 Subject: [PATCH] LUDOC-531 mdt: Added more info on DoM EOF Added details on the lfs setstripe -E option usage, with a clear explanation of the end-of-file (EOF) handling. Signed-off-by: Rajeev Mishra Change-Id: I8d828fd9e8124441afe6542e3a10e28085fe2991 Reviewed-on: https://review.whamcloud.com/c/doc/manual/+/56127 Tested-by: jenkins Reviewed-by: Andreas Dilger --- DataOnMDT.xml | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/DataOnMDT.xml b/DataOnMDT.xml index de77c39..fb7d07d 100644 --- a/DataOnMDT.xml +++ b/DataOnMDT.xml @@ -31,6 +31,30 @@ with a RAID0 layout. The OST components are not instantiated until a client writes or truncates the file beyond the size of the MDT component. + + When specifying a DoM layout, it might be assumed that the + remaning layout will automatically go to the OSTs, + but this is not the case. As with regular PFL layouts, if an + EOF component is not present, + then writes beyond the end of the last existing component will fail + with error ENODATA ("No data available"). + For example, creating a DoM file with a component end at 1 MB will + not be writable beyond 1 MiB: + +$ lfs setstripe -E 1M -L mdt /mnt/testfs/domdir +$ dd if=/dev/zero of=/mnt/testfs/domdir/testfile bs=1M +dd: error writing '/myth/tmp/pfl-mdt-only': No data available +2+0 records in +1+0 records out +1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00186441 s, 562 MB/s + + To allow the file to grow beyond 1 MB, add one or more regular + OST components with an EOF component at the end: + + +lfs setstripe -E 1M -L mdt -E 1G -c1 -E eof -c4 /mnt/testfs/domdir + +
-- 1.8.3.1