Date: Mon, 28 Jan 2013 17:49:15 -0500 From: Paul Kraus <paul@kraus-haus.org> To: FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Software raid VS hardware raid Message-ID: <5C5F6EE2-5744-48B8-B4D9-DB9E19A5FCC0@kraus-haus.org> In-Reply-To: <5106E301.4070707@itlegion.ru> References: <5106E301.4070707@itlegion.ru>
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On Jan 28, 2013, at 3:43 PM, Artem Kuchin wrote: > I have to made a decision on choosing a dedicated server. > The problem i see is that while i can find very affordable and good = options they do not > provide hardware raid or even if they do it is not the best hardware = for freebsd. I prefer SW RAID, specifically ZFS, for two very large reasons: 1) Visibility: =46rom the OS layer you have very good visibility into = the health of the RAID set and the underlying drives. All of the lower = end HW RAID solutions I have seen require proprietary software to = "manage" the RAID configuration, usually from the physical system's BIOS = layer. Finding good OS layer software to monitor the RAID and the drives = has been very painful. If you don't know you have a failure, then you = can't do anything about it and when you have a second failure you lose = data. Running a HW RAID system and not being able to issue a simple = command from the OS and see the status of the RAID scares me. 2) Error Detection and Correction: HW RAID relies on the drives to = report read and write errors. With UNCORRECTABLE error rates of 10^-14 = and 10^-15 and LARGE (1 TB plus) drives you are almost guaranteed to = statistically run into UNCORRECTABLE errors over the life of a typical = drive. ZFS has end to end checksums and can detect a single bad bit from = a drive, if the set is redundant it can recreate the correct data and = re-write it, effectively correcting the bad data on disk. NOTE: Larger, more expensive HW RAID systems address both of the above = issues, but at a much higher cost in terms of money and management = overhead. DISCLAIMER: I have been managing mission critical, cannot afford to lose = it data under ZFS for over 5 years, with no loss of data (even with some = horribly unreliable low cost HW RAID systems under the ZFS layer... if = we had not used ZFS we would have lost data multiple times). =20 -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company
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