Date: Mon, 5 Jul 2021 16:49:20 +0100 From: Pete French <petefrench@ingresso.co.uk> To: stable@freebsd.org Subject: Re: ZFS + mysql appears to be killing my SSD's Message-ID: <4b5a0367-96c2-1d3f-bcb2-a76bd66bc76e@ingresso.co.uk> In-Reply-To: <f15cfc5a-e3c0-f1a7-c123-d369db9bc199@denninger.net> References: <89c37c3e-22e8-006e-5826-33bd7db7739e@ingresso.co.uk> <2fd9b7e4-dc75-fedc-28d7-b98191167e6b@freebsd.org> <9c71d627-55b8-2464-6cc9-489e4ce98049@ingresso.co.uk> <f15cfc5a-e3c0-f1a7-c123-d369db9bc199@denninger.net>
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On 05/07/2021 16:09, Karl Denninger wrote: > As noted elsewhere assuming ashift=12 the answer on write amplification > is no. > > Geli should be initialized with -s 4096; I'm assuming you did that? Yup, I have everything defaulting to 4k sectors now, and I was hoping there was no write amplification going on if I did that. > I have a 5-unit geli-encrypted root pool, all Intel 240gb SSDs. They do > not report remaining lifetime via smart but do report indications of > trouble. Here's one example snippet from one of the drives in that pool: Thanks for this ... its inyeresting to have something to compare against. Mine are Kingston 240G drives, though some of the replacements will be Crucial (i.e. Micron) > Device Statistics (GP Log 0x04) > Page Offset Size Value Flags Description > 0x01 ===== = = === == General Statistics (rev 2) == > 0x01 0x008 4 100 --- Lifetime Power-On Resets > 0x01 0x018 6 118722148102 --- Logical Sectors Written > 0x01 0x020 6 89033895 --- Number of Write Commands > 0x01 0x028 6 93271951909 --- Logical Sectors Read > 0x01 0x030 6 6797990 --- Number of Read Commands So this is interesting, because my vaues for the machine I was describing arlier, where a drive was replaced are ada0:0x01 0x018 6 3084505072 --- Logical Sectors Written ada0:0x01 0x020 6 1219372767 --- Number of Write Commands ada0:0x01 0x028 6 1168765724 --- Logical Sectors Read ada0:0x01 0x030 6 56588781 --- Number of Read Commands ada1:0x01 0x018 6 2014784574 --- Logical Sectors Written ada1:0x01 0x020 6 68557083 --- Number of Write Commands ada1:0x01 0x028 6 41230034 --- Logical Sectors Read ada1:0x01 0x030 6 2438618 --- Number of Read Commands The replacement has more written sectors than the one which wasnt replaced. yet these are in RAID-1, so how can that be? The numbers for sectors written are way lower than yours, but the write commands are much higher. For a pair of drives in RAID-1 where ada0 has been replaced and resilvered from ada1, those looks very wrong to me. > 6 years in-use, roughly, and no indication of anything going on in terms > of warnings about utilization or wear-out. There is a MYSQL database on yes, your figures are what I expect to see, but the ones above are what I actually have. The disparity between the two halves of the RAID are bothering me, I have to say. Do you have any tuning applies to your ZFS filesystems ? I have reduced the recrodsize on the data directories to 32k to better match innodb and have turned off atime and sync. But those are things I would expect to reduce the write load, not increase it. -pete.
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