Date: Mon, 9 Jun 2008 09:44:18 +0200 (CEST) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Dan Nelson <dnelson@allantgroup.com> Cc: Ivan Voras <ivoras@freebsd.org>, freebsd-questions@freebsd.org Subject: Re: FreeBSD + ZFS on a production server? Message-ID: <20080609094333.H27092@wojtek.tensor.gdynia.pl> In-Reply-To: <20080608233315.GA33530@dan.emsphone.com> References: <1a5a68400806080604ped08ce8p120fc21107e7de81@mail.gmail.com> <20080608215648.Q9779@wojtek.tensor.gdynia.pl> <20080608230131.00003da7@westmark> <20080609001010.G59013@wojtek.tensor.gdynia.pl> <g2hp91$jtp$1@ger.gmane.org> <20080608233315.GA33530@dan.emsphone.com>
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>>> random write speeds (but still at least half of single drive). but >>> this is advertised as a feature >> >> Is this because of checksum verification (the need to read all >> components) or something else? Any documentation/references? > > RAID-Z stores a single checksum over the whole stripe, instead of > checksumming each disks's section separately, so it has to read from > all disks to validate the stripe. Only random reads are penalized, > though. random reads are most common read on unix, unless you process linearly huge files, but that's fast on UFS too.
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