Date: Thu, 21 Jun 2012 10:38:18 -0500 From: weldon@excelsusphoto.com To: <freebsd-questions@freebsd.org> Subject: Re: Is ZFS production ready? Message-ID: <c824f2f1dc18a153a1dca35b3be7f18b@excelsusphoto.com> In-Reply-To: <alpine.BSF.2.00.1206211707570.3361@wojtek.tensor.gdynia.pl> References: <4FE2CE38.9000100@gmail.com> <CAPj0R5Kmi-%2BdJ7mPvTrTAoS8O983svOyR2WyK2_v1Cr07dSS_A@mail.gmail.com> <alpine.BSF.2.00.1206211413140.2263@wojtek.tensor.gdynia.pl> <CA%2BD9QhuQ%2BbxKW9%2BdX%2BzS9mErwz8JSkV2G7qL0KfB8BH_LGJAgA@mail.gmail.com> <alpine.BSF.2.00.1206211539230.2903@wojtek.tensor.gdynia.pl> <CA%2BD9QhvR_eKtVxdKcaMyOS7tLw_AOHKgUy3o7mJn2b=chMA0Xw@mail.gmail.com> <alpine.BSF.2.00.1206211619250.3092@wojtek.tensor.gdynia.pl> <CA%2BD9QhvwKZm7heoe7tpfhYCJvkknw_HC7aFjCu%2B-1xYQBmV6ng@mail.gmail.com> <alpine.BSF.2.00.1206211644350.3170@wojtek.tensor.gdynia.pl> <CA%2BD9QhsyOh34SghWzQPpnTig%2BUmSEO2VP7jfPxTXs9zW9Uakeg@mail.gmail.com> <alpine.BSF.2.00.1206211707570.3361@wojtek.tensor.gdynia.pl>
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On 21.06.2012 10:15, Wojciech Puchar wrote: >> >> I do understand your setup but I dont have too agree that it is a >> good > > so i would repeat my question. > Assume you have 48 disks, in mirrored configuration (24 mirrors) and > 480 users with their data on them. > > Your solution with ZFS - ZFS crashes or you get double disk failure. > Assuming the latter by average one per 24 file (randomly chosen) is > destroyed which - in practice and limited time, means everything > destroyed. Actually more than one per 24 - large files can be spread > over. > > Your solution with UFS - better as there is fsck which slowly but > successfully repairs problem. with double disk failure - the same! > > > You restore everything from backup (i assume you have one). This > takes like a day or more, one or two complete work days lost+all > users > in practice lost everything since last backup. > > My solution with UFS - fsck in case of failure work in parallel on 24 > disks so not that long. double disk failure means losing data of 1/24 > users. > > every one per 24 user cannot work, others work and i without any > stress do recover this 1/24 of users data from backup after putting > replacement disks. > > 1/24 of users lost data since last backup, and some hours of time. > > > Even assuming ZFS is perfect then we both have problems as often, but > my problems are 1/24 as severe as yours. > > I think it is incorrect to assume that a failure with ZFS that cannot be recovered could be recovered if you used UFS with fsck. What fsck fixes in other file systems doesn't apply to ZFS by ZFS's design. fsck deals with fixing superblock inconsistancies on non-journaled file systems (like UFS/UFS2), not resurecting corrupted blocks on a disk. http://www.c0t0d0s0.org/archives/6071-No,-ZFS-really-doesnt-need-a-fsck.html http://en.wikipedia.org/wiki/Fsck http://en.wikipedia.org/wiki/UFS2
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