On Tue, Feb 16, 2010 at 6:47 PM, Christo Kutrovsky <kutrov...@pythian.com>wrote:
> Just finished reading the following excellent post: > > http://queue.acm.org/detail.cfm?id=1670144 > > And started thinking what would be the best long term setup for a home > server, given limited number of disk slots (say 10). > > I considered something like simply do a 2way mirror. What are the chances > for a very specific drive to fail in 2 way mirror? What if I do not want to > take that chance? > > I could always put "copies=2" (or more) to my important datasets and take > some risk and tolerate such a failure. > > But chances are, everything that is not copies=2 will have some data on > those devices, and will be lost. > > So I was thinking, how can I limit the damage, how to inject some kind of > "damage control". > > One of the ideas that sparkled is have a "max devices" property for each > data set, and limit how many mirrored devices a given data set can be spread > on. I mean if you don't need the performance, you can limit (minimize) the > device, should your capacity allow this. > > Imagine this scenario: > You lost 2 disks, and unfortunately you lost the 2 sides of a mirror. > > You have 2 choices to pick from: > - loose entirely Mary, Gary's and Kelly's "documents" > or > - loose a small piece of Everyone's "documents". > > This could be implement via something similar to: > read/write property "target device spread" > read only property of "achieved device spread" as this will be size > dependant. > > Opinions? > > raid is not designed to protect data, its designed to ensure uptime, if you can't afford to loose the data, then you should back it up, daily, and store more than one copy, with at least one copy being off site. If your site burns to the ground your data is gone no matter how many disks you have in the system. after this you should allocate a number of hot spares to the system should one fail. If you are truly paranoid, 3-way mirror can be used. then you can loose 2 disks without a loss of data. Spread disks across multiple controllers, and get disks from different companies and different lots to less the likely hood of getting hit by a bad batch taking out your pool. replace disks early as soon as you see disk errors. And above all backup all data you can't afford to loose. James Dickens http://uadmin.blogspot.com > Remember. The goal is damage control. I know 2x raidz2 offers better > protection for more capacity (altought less performance, but that's no the > point). > -- > This message posted from opensolaris.org > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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