not really on topic, but a fun little site detailing some disk vibrating issues
http://blogs.sun.com/brendan/entry/unusual_disk_latency On Tue, Jun 15, 2010 at 3:10 PM, james <[email protected]> wrote: > 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 > -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
