Messages in this thread | | | Date | Tue, 16 Jul 2013 01:22:28 -0700 (PDT) | From | David Lang <> | Subject | Re: 3.10: discard/trim support on md-raid1? |
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Part of this depends on the exact failure mode. I've seen cases where drives fail, and the drive does a bunch of retries, then the OS does a bunch of retries, and eventually the read fails, but in the meantime, everything stalls for a long time.
I've even seen the same thing in at least one case where there was a hardware RAID card in use.
David Lang
On Tue, 16 Jul 2013, Justin Piszcz wrote:
> Thanks for the replies, > > After some further testing.. > When I ran a repair on the md's sync_action, the system would reduce > I/O to the RAID-1 to 14kb/s or even less when it hit a certain number > of blocks and effectively locked the system every time. > It turned out to be a bad SSD (it also failed Intel's Secure Erase), I RMA'd it. > Interesting though that it did not drop out of the array but froze the > system (the failure scenario was odd). > > Justin. > > > > On Tue, Jul 16, 2013 at 3:15 AM, NeilBrown <neilb@suse.de> wrote: >> On Sat, 13 Jul 2013 06:34:19 -0400 "Justin Piszcz" <jpiszcz@lucidpixels.com> >> wrote: >> >>> Hello, >>> >>> Running 3.10 and I see the following for an md-raid1 of two SSDs: >>> >>> Checking /sys/block/md1/queue: >>> add_random: 0 >>> discard_granularity: 512 >>> discard_max_bytes: 2147450880 >>> discard_zeroes_data: 0 >>> hw_sector_size: 512 >>> iostats: 0 >>> logical_block_size: 512 >>> max_hw_sectors_kb: 32767 >>> max_integrity_segments: 0 >>> max_sectors_kb: 512 >>> max_segment_size: 65536 >>> max_segments: 168 >>> minimum_io_size: 512 >>> nomerges: 0 >>> nr_requests: 128 >>> optimal_io_size: 0 >>> physical_block_size: 512 >>> read_ahead_kb: 8192 >>> rotational: 1 >>> rq_affinity: 0 >>> scheduler: none >>> write_same_max_bytes: 0 >>> >>> What should be seen: >>> rotational: 0 >> >> What has "rotational" got to do with "supports discard"? >> There may be some correlation, but it isn't causal. >> >>> And possibly: >>> discard_zeroes_data: 1 >> >> This should be set as the 'or' of the same value from component devices. And >> does not enable or disable the use of discard. >> >> I don't think that "does this device support discard" appears in sysfs. >> >> I believe trim does work on md/raid1 if the underlying devices all support it. >> >> NeilBrown >> >> >> >>> >>> Can anyone confirm if there is a workaround to allow TRIM when using >>> md-raid1? >>> >>> Some related discussion here: >>> http://us.generation-nt.com/answer/md-rotational-attribute-help-206571222.ht >>> ml >>> http://www.progtown.com/topic343938-ssd-strange-itself-conducts.html >>> >>> >>> Justin. >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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