Hello, accroding to red hat documentation "smaller is better". I personaly use 1TB volumes with 256MB journal
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html-single/Global_File_System_2/index.html#s1-formatting-gfs2 S pozdravem Kristián Feldsam Tel.: +420 773 303 353, +421 944 137 535 E-mail.: supp...@feldhost.cz www.feldhost.cz - FeldHost™ – profesionální hostingové a serverové služby za adekvátní ceny. FELDSAM s.r.o. V rohu 434/3 Praha 4 – Libuš, PSČ 142 00 IČ: 290 60 958, DIČ: CZ290 60 958 C 200350 vedená u Městského soudu v Praze Banka: Fio banka a.s. Číslo účtu: 2400330446/2010 BIC: FIOBCZPPXX IBAN: CZ82 2010 0000 0024 0033 0446 > On 26 Aug 2017, at 08:11, Gionatan Danti <g.da...@assyoma.it> wrote: > > Hi list, > I am evaluating how to refresh my "standard" cluster configuration and GFS2 > clearly is on the table ;) > > GOAL: to have a 2-node HA cluster running DRBD (active/active), GFS2 (to > store disk image) and KVM (as hypervisor). The cluster had to support live > migration, but manual failover is sufficient (ie: if something goes wrong, is > ok to require a sysadmin to take action to restore services). > > The idea is to, by default, always run VMs on the first host (using virtlock > or sanlock to deny the starting of the same virtual machine from the second > host). Should anything bad happen, or should the first host be in maintenance > mode, the VMs can be migrated/restarted on the second host. > > I have a few questions: > > - other peoples told me GFS2 is not well suited for such a tasks and that I > am going to see much lower performance than running on a local filesystem > (replicated via other means). This advice stems from the requirement to > maintain proper write ordering, but strict cache coherency also between the > hosts. However, from what I understand reading GFS2 documentation, when > operating mostly on a single host (ie: not running anything on the second > node), the overhead should be negligible. I am right, or orribly wrong? > > - reading RedHat documentation here[1], I see that it is strongly advised to > set cache=none for any virtual disk. Is this required from proper operation, > or it is "only" a performance optimization to avoid what stated above (ie: > two host sharing the same data in pagecache, thus requiring coherency > traffic)? As I really like the improved performance with cache=writeback > (which, by the virtue of barrier passing, comes without data loss concerns), > you think it is safe to use writeback in production? > > - I plan to have a volume of about 8 or 16 TB. I understand that GFS2 is > tested with much bigger volumes (ie: 100 TB), but I would ask: do you would > trust a TB-sized volume on GFS2? What about fsck? It works well/reliably? > > - I plan to put GFS2 on top of LVM (for backup snapshot) and replicate the > volume with DRBD2. Do you see any drawback in this approach? > > - finally, how do you feel about running your production virtual machines on > DRBD + GFS2? > > Thank you all. > > [1] > https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html-single/Global_File_System_2/index.html#s1-VMsGFS2-gfs2 > > -- > Danti Gionatan > Supporto Tecnico > Assyoma S.r.l. - www.assyoma.it > email: g.da...@assyoma.it - i...@assyoma.it > GPG public key ID: FF5F32A8 > > -- > Linux-cluster mailing list > Linux-cluster@redhat.com > https://www.redhat.com/mailman/listinfo/linux-cluster
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