From: Wols Lists <antlists@youngman.org.uk>
To: Alireza Haghdoost <alireza@cs.umn.edu>,
Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>
Cc: Dan Williams <dan.j.williams@intel.com>, Shaohua Li <shli@fb.com>,
Neil Brown <neilb@suse.de>,
linux-raid <linux-raid@vger.kernel.org>,
Song Liu <songliubraving@fb.com>,
Kernel-team@fb.com
Subject: Re: [RFC] raid5: add a log device to fix raid5/6 write hole issue
Date: Wed, 01 Apr 2015 20:57:30 +0100 [thread overview]
Message-ID: <551C4DAA.4010701@youngman.org.uk> (raw)
In-Reply-To: <CAB-428nVCN=5au0jONamXORNZ656UZ1Ecgrk-paArruX9tpHJQ@mail.gmail.com>
On 01/04/15 19:46, Alireza Haghdoost wrote:
>> Now, how can be assured, in that case, that the "cache"
>> > device is safe after the power is restored?
> You do sync write-ahead logging on the Flash cache. If it return
> successful, you do fire the writes to the RAID. If system crash/fails
> during the RAID writes (Write-hole), you just recover data by scanning
> write-ahead log in the flash cache and replay the logs into the RAID
> drives.
>
Just to throw something nasty into the mix, I'm not sure whether it's
SSDs or SD-cards, but there certainly *was* a spate of corrupted
*controllers*.
In other words, a power failure would RELIABLY TRASH the device, if it
happened at the wrong moment. Hopefully that's been fixed ...
Cheers.
Wol
next prev parent reply other threads:[~2015-04-01 19:57 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-30 22:25 [RFC] raid5: add a log device to fix raid5/6 write hole issue Shaohua Li
2015-04-01 3:47 ` Dan Williams
2015-04-01 5:53 ` Shaohua Li
2015-04-01 6:02 ` NeilBrown
2015-04-01 17:14 ` Shaohua Li
2015-04-01 18:36 ` Piergiorgio Sartor
2015-04-01 18:46 ` Dan Williams
2015-04-01 20:07 ` Jiang, Dave
2015-04-01 18:46 ` Alireza Haghdoost
2015-04-01 19:57 ` Wols Lists [this message]
2015-04-01 20:04 ` Alireza Haghdoost
2015-04-01 20:18 ` Wols Lists
2015-04-01 20:17 ` Jens Axboe
2015-04-01 21:53 ` NeilBrown
2015-04-01 23:40 ` Shaohua Li
2015-04-02 0:19 ` NeilBrown
2015-04-02 4:07 ` Shaohua Li
2015-04-09 0:43 ` Shaohua Li
2015-04-09 5:04 ` NeilBrown
2015-04-09 6:15 ` Shaohua Li
2015-04-09 15:37 ` Dan Williams
2015-04-09 16:03 ` Shaohua Li
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