Date: Tue, 01 Dec 2009 09:38:22 +1100 From: Andrew Snow <andrew@modulus.org> To: Zaphod Beeblebrox <zbeeble@gmail.com>, freebsd-fs@freebsd.org Subject: Re: ZFS guidelines - preparing for future storage expansion Message-ID: <4B14495E.7050306@modulus.org> In-Reply-To: <5f67a8c40911301233s46a2818at9051c4ebbacf7e25@mail.gmail.com> References: <2ae8edf30911300120x627e42a9ha2cf003e847d4fbd@mail.gmail.com> <4B139AEB.8060900@jrv.org> <2ae8edf30911300425g4026909bm9262f6abcf82ddcd@mail.gmail.com> <5f67a8c40911301233s46a2818at9051c4ebbacf7e25@mail.gmail.com>
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Zaphod Beeblebrox wrote: > I moved from 5x 750G to 5x 1.5T disks this way earlier this year. It takes > a _long_ time. resilvering 750g (they were about 98% full when I did this) > onto the 1.5T disks took about 12 hours each. Currently there is no "read-ahead" for scrubbing and resilvering, so it only talks to one disk and at a time and proceeds using only about half the I/O capacity of your disks (or less). Read-ahead is one of the planned features for ZFS next year. Also, when your disks are 98% or more full and you are doing any writes at all ZFS spends a long time looking for free blocks with an inefficient algorithm. An improved "disk full" algorithm is also planned for next year. - Andrew
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