> From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Bill Moran > Sent: Friday, November 23, 2007 3:28 PM > To: Jan Catrysse > Cc: freebsd-questions@freebsd.org > Subject: Re: RAID1 synchronisation - howto OR not necessary? > > "Jan Catrysse" <[EMAIL PROTECTED]> wrote: > > Hi Bill, > > > > Thank you for your input. > > > > I assumed this was common knowledge, but I can be wrong? > > I've checked some other RAID controllers in the company and all of > > them have the need to be verified/synchronized once and a while. > > No. > > There is a _world_ of difference between "verify" and "synchronize". > Periodically verifying the health of a RAID array is good practice. > Re-synchronizing it periodically is stupid. If you have to > do that, then you wasted money on a RAID card. > > > This > > happens in the BIOS for the more expensive cards (> 600€) > and with a > > utility/driver for the low budget cards... > > Depends on what you're talking about. > > Yes, expensive cards do both health checking and resyncing in > the BIOS without the need of operator intervention. > > Low-end hot-swappable cards will automatically do the > resynchronizing if they detect a HDD change, but often don't > do periodic health checking. > > Low-end cards do neither. However, you have to power the > machine down to replace a failed drive, so you're also > accepting the burden of waiting for the BIOS to resync. It's > part of the cost trade-off. > > > This is what I found in a 3Ware manual: > > Verification can provide early warning of a disk drive > problem or failure. > > ...verification once every 24 hours... > > Not verifying the unit periodically can lead to an unstable > array unit and may cause data loss. > > It is strongly recommended that you schedule a verify at > least 1 time per week. > > Nice documentation ... Do you verify every 24 hours or once a week? > > In any event, the availability of such a utility for FreeBSD > depends on the driver and the (possible) availability of > third-party (or even > vendor-supplied) utilities. For example, LSI provides the > megaraid utility. It's designed for Linux but works on > FreeBSD and allows total control over the RAID card, > including verifications. Reading the man page for the driver > being used may turn up something. > > I don't know if one exists for your specific card, but keep > in mind that the driver you're using may also work with > high-end RAID systems that don't need it, so the absence of > one is possible. > > I suggest you reformat/repost your question with a subject > line more along the lines of "Looking for a control utility > for ICH8R RAID" It's quite possible that the people who know > a lot about that hardware missed the original conversation thread. > > If there is no such utility, I suggest looking into something > like samhain, which will continually validate that the files > on your system are uncorrupted. This has the added advantage > of warning you if someone has cracked your system and > installed a trojan. > > Also consider the benefit of spending the extra $$ on a > high-end RAID card. There are very good reasons that people > are willing to pay more for them. Personally, I wouldn't use > a low-end RAID card ... GEOM would be just as good if not > better, IMHO.
Hello again, I understand what you mean by synchronization not beeing the same as data verification. What I mean is indeed data verification. For the Intel ICH8R controller FreeBSD uses ATA(4), no vendor support is available. It is possible however to control the array using ATACONTROL STATUS / DETACH / ADDSPARE / REBUILD / ... but no VERY command seem to exist. As you suggest I will repost the question with another subject. Would it be a big problem if I contact the FreeBSD developper of ATA(4) directly? I didn't dig in GEOM because I wondered what happens if the primary disk fails when two disks are in a RAID1 config? Cheers, Jan _______________________________________________ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
