Date: Tue, 17 May 2016 12:44:50 +0200 From: "Ronald Klop" <ronald-lists@klop.ws> To: "FreeBSD Filesystems" <freebsd-fs@freebsd.org>, "Rainer Duffner" <rainer@ultra-secure.de> Subject: Re: zfs receive stalls whole system Message-ID: <op.yhlr40k3kndu52@ronaldradial.radialsg.local> In-Reply-To: <0C2233A9-C64A-4773-ABA5-C0BCA0D037F0@ultra-secure.de> References: <0C2233A9-C64A-4773-ABA5-C0BCA0D037F0@ultra-secure.de>
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On Tue, 17 May 2016 01:07:24 +0200, Rainer Duffner <rainer@ultra-secure.de> wrote: > Hi, > > I have two servers, that were running FreeBSD 10.1-AMD64 for a long > time, one zfs-sending to the other (via zxfer). Both are NFS-servers and > MySQL-slaves, the sender is actively used as NFS-server, the recipient > is just a warm-standby, in case something serious happens and we don’t > want to wait for a day until the restore is back in place. The > MySQL-Slaves are actively used as read-only servers (at the application > level, Python’s SQL-Alchemy does that, apparently). > > They are HP DL380G8 (one CPU, hexacore) with over 128 GB RAM (I think > one has 144, the other has 192). > While they were running 10.1, they used HP P420 RAID-controllers with > individual 12 RAID0 volumes that I pooled into 6-disk RAIDZ2 vdevs. > I use zfsnap to do hourly, daily and weekly snapshots. > > Sending worked well, especially after updating to 10.1 > > Because the storage was over 90% full (and I really hate this > RAID0-business we have with the HP RAID controllers), I rebuilt the > servers with HPs OEMed H220/221 controllers (LSI 2308 in disguise) and > an external disk shelf, hosting 12 additional disks was added- and I > upgraded to FreeBSD 10.3. > Because we didn’t want to throw out the original disks, but increase > available space a lot, the new disks are double the size of the original > disks (600 vs. 1200 GB SAS). > I also created GPT-partitions on the disks and labeled them according to > the disk’s position in the cages/shelf, created the pools with the > got-partition-names instead of the daX-names. > > Now, when I do a zxfer, sometimes the whole system stalls while the data > is sent over, especially if the delta is large or if something else is > reading from the disk at the same time (backup agent). > > I had this before, on 10.0 (I believe, we didn’t have this in 9.1 > either, IIRC) and it went away in 10.1. > > It’s very difficult (well, impossible) to debug, because the system > totally hangs and doesn’t accept any keypresses. > > Would a ZIL help in this case? > I always thought that NFS was the only thing that did SYNC writes… Databases love SYNC writes too. (But that doesn't say anything about the unresponsive system). I think there is a statistic somewhere in FreeBSD to analyze the sync vs async writes and decide if a ZIL will help or not. (But that doesn't say anything about the unresponsive system either). Ronald.
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