Date: Wed, 28 Nov 2012 15:07:33 +0100 From: "O. Hartmann" <ohartman@zedat.fu-berlin.de> To: Olivier Smedts <olivier@gid0.org> Cc: Current FreeBSD <freebsd-current@freebsd.org> Subject: Re: ZFS: ZIL with only one additional disk and how secure? Message-ID: <50B61AA5.7030007@zedat.fu-berlin.de> In-Reply-To: <CABzXLYNgUC1GVc7xMQs1m68XhKzVw3QsXjQxevW8ZP3Sw6aTDQ@mail.gmail.com> References: <50B611B6.40903@zedat.fu-berlin.de> <CABzXLYNgUC1GVc7xMQs1m68XhKzVw3QsXjQxevW8ZP3Sw6aTDQ@mail.gmail.com>
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[-- Attachment #1 --] On 11/28/12 14:38, Olivier Smedts wrote: > Hi, > > 2012/11/28 O. Hartmann <ohartman@zedat.fu-berlin.de>: >> Hello, >> I have a naive question. >> I read about speeding up NFSv4 shared ZFS array. I use a RAIDZ1 volume >> made up from 5 times 3TB harddrives, attached to a ICH10 SATA controller >> on a FreeBSD 10.0-CURRENT box. The maximum performance of that array >> never goes beyond 45 - 51 MB/s and levels out very often at 12 - 35 MB/s >> when used as a NFSv4 share and 1 GBit LAN. The local system harddisk, >> attached to the sixth SATA port of the same controller and containig a >> UFS2 filesystem, is capable of doing tasks with 60 - 80 MB/s (peak) when >> used as a NFSv4 share with another FreeBSD 10.0-CURRENT box. >> >> I used several reported tweaks on the RAIDZ1 ZFS volume exporting it as >> a NFSv4 volume, so I was capable of raising the throughput from sad 3 >> MB/s up to the 30 MB/s sustained. >> >> Also I was told that adding a dedicated ZIL drive could speed up things >> up to 90 MB/s with the mentioned construction of a RAIDZ1 over NFSv4. It >> is always suggested to add SSDs, a pair, for security reasons. >> >> My question in conrete is now: Do I need two (2) ZIL drives in a mirror? >> I guess this is considered due to security issues which lead to the next >> question: If it is possible to use only one ZIL drive and this drive >> gets corrupted, is the whole ZFS array corrupted, then? > > You don't "need" two because if the ZIL is corrupted you'll only loose > the data since the last TXG, but no metadata. Make sure you have an > up-to-date pool. > > But you'll *need* a battery cache or supercaps on the SSD(s) so that > they flush their caches in case of a power failure. > >> The minor question regards to the use of SSDs: Is it possible to gain >> speedup also from an ordinary disk dedicated to the ZFS array connected >> to a additional SATA controller? The SATA controller should be fast >> enough to serve a bandwith of 90 - 100 MB/s (theoretically) over 1 GBit >> lines when using the ZFS array as a NFSv4 export (the LAN is limiting, >> so, but 80 - 90 MB/s is possible on the specific box, the limiting >> factor at the moment is the bad performance of ZFS). > > I don't think so, or not much. What makes SSDs appealing for ZIL is > that they have very good access times / latencies. > >> The box is a quad core system at 3 GHz (Intel Q6600) with 8 GB of RAM >> running most recent FreeBSD 10.0-CURRENT/amd64. >> >> Thanks in advance, >> >> Oliver > > Cheers > Good to hear. Thanks a lot, Greetings Oliver [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iQEcBAEBAgAGBQJQthqpAAoJEOgBcD7A/5N8uSQH/RgbZCkeB9LWb6elghfMhOyn yZ+drgWuuBBUi63Ov5WuA9IBNBCBoRqGctiO2TcqnmdyFtMUeqcB5LaoeN+60XIv GBp3+fZmIrJPZCYFiFFiJp3wqX1Mc9fXfmvoLy/FuPjJiAQ8VFbNFWsWlgLXHIIy 7ABvxClgF42fmC/N8cFlNnZ9Ms7gd55bQ/DUdEt5FDjAF5ylJF1y0dggsSQNDbYE cCV5/R1BLCSsaSjea44228vQu93VQyUED1lqiNrW9z6v1gns1maMlRtb3Nq7w6Gh GBmOnB3gP4GCXJFWE+62gAwna3TpMZfjVF+y+fVx1b2Eh4PNAPGouU2lsduealY= =ufi5 -----END PGP SIGNATURE-----help
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