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Detect a slow raidz child during reads

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A single slow responding disk can affect the overall read
performance of a raidz group.  When a raidz child disk is
determined to be a persistent slow outlier, then have it
sit out during reads for a period of time. The raidz group
can use parity to reconstruct the data that was skipped.

Each time a slow disk is placed into a sit out period, its
`vdev_stat.vs_slow_ios count` is incremented and a zevent
class `ereport.fs.zfs.delay` is posted.

The length of the sit out period can be changed using the
`raid_read_sit_out_secs` module parameter.  Setting it to
zero disables slow outlier detection.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Contributions-by: Don Brady <don.brady@klarasystems.com>
Contributions-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17227
This commit is contained in:
Paul Dagnelie
2025-08-27 16:41:48 -07:00
committed by Brian Behlendorf
parent 0620c979a5
commit d64711c202
28 changed files with 1399 additions and 13 deletions
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module/zfs/vdev_draid.c
+28
View File
@@ -22,6 +22,7 @@
/*
* Copyright (c) 2018 Intel Corporation.
* Copyright (c) 2020 by Lawrence Livermore National Security, LLC.
* Copyright (c) 2025, Klara, Inc.
*/
#include <sys/zfs_context.h>
@@ -1996,6 +1997,33 @@ vdev_draid_io_start_read(zio_t *zio, raidz_row_t *rr)
rc->rc_allow_repair = 1;
}
}
if (vdev_sit_out_reads(cvd, zio->io_flags)) {
rr->rr_outlier_cnt++;
ASSERT0(rc->rc_latency_outlier);
rc->rc_latency_outlier = 1;
}
}
/*
* When the row contains a latency outlier and sufficient parity
* exists to reconstruct the column data, then skip reading the
* known slow child vdev as a performance optimization.
*/
if (rr->rr_outlier_cnt > 0 &&
(rr->rr_firstdatacol - rr->rr_missingparity) >=
(rr->rr_missingdata + 1)) {
for (int c = rr->rr_cols - 1; c >= rr->rr_firstdatacol; c--) {
raidz_col_t *rc = &rr->rr_col[c];
if (rc->rc_error == 0 && rc->rc_latency_outlier) {
rr->rr_missingdata++;
rc->rc_error = SET_ERROR(EAGAIN);
rc->rc_skipped = 1;
break;
}
}
}
/*