| 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.: support@xxxxxxxxxxx
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.danti@xxxxxxxxxx> 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.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
--
Linux-cluster mailing list
Linux-cluster@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/linux-cluster
|
--
Linux-cluster mailing list
Linux-cluster@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/linux-cluster
