On 16/09/15 04:44, Alex wrote:
Hi,
I have a fedora22 system and would like to build a backup server. I
have four 3TB SATA disks and would like to build a RAID5 array. I
understand rebuild times can be extensive, possibility creating a
scenario where another disk fails during that rebuild time, but I'm
not sure I want to lose the extra space with creating a RAID6 array. I
believe RAID5 also has faster write speeds?
What disks are you using? Are they proper raid disks? A 12TB array can
have a soft read error every complete pass, and still be within the
disk-manufacturer's specs. If your disks are not raid-compliant, this
will stop your array from rebuilding, ever!
All four are WD30EFRX-68EUZN0. They're not the cheapest WD disks, but
they're also not the ones with the 5yr warranty. The last array I
built using disks with 5yr warranty exceeded their capacity before the
warranty expired.
Umm, 1st google result showed this:
http://community.wd.com/t5/Desktop-Mobile-Drives/New-WD30EFRX-Red-Drive-Idle3-Timer-Set-to-8-Seconds-High-LCC-in/td-p/648821/page/5
You might want to verify that setting before using in production, and
probably a quick search/read on any other issues.
(Chances are, your disks are above spec and won't give a problem. Do you
want to take the risk?)
There's always going to be some kind of risk, but I'm hoping someone
with the technical understanding about disk failure rates can tell me
if it's a prudent decision or not.
That depends on your requirements. What are the implications (for you)
if all the data is lost because two drives failed close to the same
time? Is that resulting cost more or less than getting a fourth drive
and using RAID6?
Is a 9TB RAID5 partition too risky in terms of rebuild time?
What's the preferred filesystem for a backup server these days? Should
I use XFS or ext4?
Throwing something completely different into the mix, how about
considering btrfs? It's not 100% solid yet, so you need to be careful
with it, but if you back up with rsync and the "in place" option, it'll
give you full backups for the cost of incremental.
I'm not sure I'm ready for something so experimental.
I am in fact using the hard-link function of rsync to perform backups,
though. We have a pretty robust perl script that's evolved over time.
I was also thinking of implementing bacula, but not sure I have the
time to figure it out right now.
Take a look at BackupPC (on sourceforge). It is a "perl script" that
uses rsync plus hardlinks, but also does a whole lot more. It has worked
very well for me for a number of years.
Personally, I'm also still waiting for a more "stable" version of btrfs
or equivalent which can do block level de-dupe.
Regards,
Adam
--
Adam Goryachev Website Managers www.websitemanagers.com.au
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