Thanks, Chris! On Thu Mar02'23 02:49:49PM, Chris Adams wrote: > From: Chris Adams <linux@xxxxxxxxxxx> > Date: Thu, 2 Mar 2023 14:49:49 -0600 > To: users@xxxxxxxxxxxxxxxxxxxxxxx > Reply-To: Community support for Fedora users <users@xxxxxxxxxxxxxxxxxxxxxxx> > Subject: Re: software or hardware raid? > > Once upon a time, Ranjan Maitra <mlmaitra@xxxxxxx> said: > > Thanks to everybody. I recall discussion from several years ago on the benefits of software over hardware RAID. I had completely forgotten about UPS for this new machine. Btw, what happens if power goes out (and I do not have UPS)? > > Linux software RAID keeps a bitmap of pending writes by default, which > is an okay (but not perfect) mechanism to recover from unexpected > shutdown. There's also an option to keep a write journal instead, but > unless you put that on a separate fast device (e.g. quality SSD with > long write lifetime), it'll impact performance significantly. > > There are trade-offs between various types of SW and HW RAID, so really > the first question would be "what are your requirements and > expectations". Are you talking about a high-uptime server, or a desktop > where you just want to make hardware failure less annoying? RAID (HW or > SW) is NOT backups, so you shouldn't depend on it for saving your > data. Thanks, this will be a fairly high uptime machine (not allowed to call it a server here, because that is central IT's role to have and administer:-), running lots of jobs at least a large part of the time, but the RAID will be on the /. It is more to keep the machine going if one of the two / drives fail (and till such time as I can get and put in a new one). For /home (which is where my data reside), I have 2 backups done using rsync every hour. I plan to copy the actual /home to the second one, and I was thinking that the third one would be incremental backup (kept for a year, since I occasionally realize weeks and months later that I really want a file back from long ago) or so. > > HW RAID has some advantages - quality controllers will have > battery-backed cache, so things like write journaling don't impact > performance and recovery from unexpected power failures is basically > instantaneous. For high performance requirements, there's less overhead > with HW RAID (because data only has to transit the bus once, then the > RAID controller has its own paths to the drives). But HW RAID typically > requires odd and/or proprietary software to manage, detect failures, > etc. Depending on the RAID level you are using, recovery from a failure > of the controller itself can be harder too. > > > Btw, I still stick to ext4, largely because of inertia (and because I have used lvm in the past and hated its naming conventions, I think, but there were also other limitations that I do not now recall) and have stayed away from zfs or btrfs or lvm. I am not sure what to do now. Clearly, things have moved far on. > > I'm generally in the XFS on LVM (on SW mdraid when needed) camp > myself... LVM adds a significant layer of flexibility and ability, but > still using more "traditional" filesystems like XFS and ext4. I had > poor experiences with ZFS at a former job, and am still a little leery > of some of the approach BTRFS takes. > > I'm playing with adding the dm-integrity layer for my SW mdraid (so then > XFS on LVM on mdraid on integrity on drive) setup as an additional check > against silent drive failures, but again, unless you put that data on a > separate fast SSD, it slows down performance a lot. I see, so your recommendation is to go for xfs? Many thanks again, and best wishes, Ranjan _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
