On Tuesday 15 June 2010 12:15:52 you wrote: > On Tue, Jun 15, 2010 at 11:14:38AM +0800, james wrote: > > The stuff below is interesting and a reference, but this highlights my > > favourite rant: Seagate's 'ATA more than an interface' says multiple > > disks in a machine *will* result in a higher failure rate, maybe much > > higher. > > Due to heat, or what? That paper seems to concern itself primarily with the > differences between PS (personal storage) drives and ES (enterprise > storage), in order to justify why the SCSI drives have so much higher cost > per bit.
The bit that says: Disk#1 seeks knocking Disk#2, Disk#3 off track so Disk#2 seeks knocking (mechanical coupling) Disk#1 off track so Disk#1 seeks again etc my own experience is that n-disk arrays fail more than n times 1 disk but that is oh so subjective, and so subject to the ravages of stats. James > The only mention I could see about multiple disks affecting failure rate > was "A high density server rack with many disc drives grouped close > together may experience much higher temperatures than a single drive > mounted in a desktop computer". Nothing about whether multiple disks in a > machine affect failure rate for any reason other than high temperature > (which is usually controlled in server environments). > > > So raid is a less worse option than LVM. Heed the advice in slug talks > > about backup (Sorry Sonia and Margurite, I don't remember who presented > > them) > > Yes. > > > It is possible, but not likely that *every* file on your disks is > > distributed over all 3 disks, so worst cast is that you lost 1/3 of every > > file you have. > > Only if the Logical Volume is defined with striping (the -i argument to > lvcreate). > > Rule #1 is always ... make backups. > > After that: > > - RAID1 can reduce the impact of a single-drive failure > > - RAID5 will increase the impact of failures > > - When combining multiple disks into a large Volume Group (VG), it is > possible to create Logical Volumes within the VG so that they do not span > physical devices. That way, if a disk dies (or 2, in a RAID1 setup) the > entire VG contents will not be lost, only those filesystems on the failing > devices. Hence it is a good idea to make multiple filesystems sized > according to need. > > - Make multiple types of backups: backup to HDD (on a different server), > offsite backup, Internet backup, incremental backups, DVD backups, > external HDDs are dirt cheap these days. > > - Separate data according to importance and increase the redundancy level > for the most important data. Data which is unimportant or can be recreated > need not be backed up at all. Precious data might have multiple backups to > onsite, offsite and write-once media. > > Nick. > -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
