[ClusterLabs] Antw: [EXT] DRBD Dual Primary Write Speed Extremely Slow

[Vladislav Bogdanov]

Hi

On Mon, 2022-11-14 at 15:00 +0100, Tyler Phillippe via Users wrote:
> Good idea! I setup a RAM disk on both of those systems, let them
> sync, added it to the cluster. 
> 
> One thing I left out (which didn't hit me until yesterday as a
> possibility) is that I have the iSCSI LUN attached to two Windows
> servers that are acting as a Scale-Out File Server. When I copied a
> file over to the new RAMdisk LUN via Scale-Out File Server, I am
> still getting 10-20MB/s; however, when I create a large file to the
> underlying, shared DRBD on those CentOS machines, I am getting about
> 700+MB/s, which I watched via iostat. So, I guess it's the Scale-Out
> File Server causing the issue. Not sure why Microsoft and the Scale-
> Out File Server is causing the issue - guess Microsoft really doesn't
> like non-Microsoft backing disks
> 


Not with Microsoft, but with overall iSCSI performance. For the older
iSCSI target - IET - I used to use the following settings:
InitialR2T=No 
ImmediateData=Yes 
MaxRecvDataSegmentLength=65536 
MaxXmitDataSegmentLength=65536 
MaxBurstLength=262144 
FirstBurstLength=131072 
MaxOutstandingR2T=2 
Wthreads=128 
QueuedCommands=32

Without that iSCSI LUNs were very slow independently of backing device
speed.
Probably LIO provides a way to set them up as well.

Best,
Vladislav

> Does anyone have any experience with that, perhaps? Thanks!!
> 
> Respectfully,
>  Tyler
> 
> 
> 
> Nov 14, 2022, 2:30 AM by Ulrich.Windl at rz.uni-regensburg.de:
> > Hi!
> > 
> > If you have planty of RAM you could configure an iSCSI disk using a
> > ram disk and try how much I/O you get from there.
> > Maybe you issue is not-su-much DRBD related. However when my local
> > MD-RAID1 resyncs with about 120MB/s (spinning disks), the system
> > also is hardly usable.
> > 
> > Regards,
> > Ulrich
> > > > > Tyler Phillippe via Users <users at clusterlabs.org> schrieb am
> > > > > 13.11.2022 um
> > 19:26 in Nachricht <NGmE_x7--3-9 at tutamail.com>:
> > > Hello all,
> > > 
> > > I have setup a Linux cluster on 2x CentOS 8 Stream machines - it
> > > has 
> > > resources to manage a dual primary, GFS2 DRBD setup. DRBD and the
> > > cluster 
> > > have a diskless witness. Everything works fine - I have the dual
> > > primary DRBD 
> > > working and it is able to present an iSCSI LUN out to my LAN.
> > > However, the 
> > > DRBD write speed is terrible. The backing DRBD disks (HDD) are
> > > RAID10 using 
> > > mdadm and they (re)sync at around 150MB/s. DRBD verify has been
> > > limited to 
> > > 100MB/s, but left untethered, it will get to around 140MB/s. If I
> > > write data 
> > > to the iSCSI LUN, I only get about 10-15MB/s. Here's the DRBD 
> > > global_common.conf - these are exactly the same on both machines:
> > > 
> > > global {
> > > usage-count no;
> > > udev-always-use-vnr;
> > > }
> > > 
> > > common {
> > > handlers {
> > > }
> > > 
> > > startup {
> > > wfc-timeout 5;
> > > degr-wfc-timeout 5;
> > > }
> > > 
> > > options {
> > > auto-promote yes;
> > > quorum 1;
> > > on-no-data-accessible suspend-io;
> > > on-no-quorum suspend-io;
> > > }
> > > 
> > > disk {
> > > al-extents 4096;
> > > al-updates yes;
> > > no-disk-barrier;
> > > disk-flushes;
> > > on-io-error detach;
> > > c-plan-ahead 0;
> > > resync-rate 100M;
> > > }
> > > 
> > > net {
> > > protocol C;
> > > allow-two-primaries yes;
> > > cram-hmac-alg "sha256";
> > > csums-alg "sha256";
> > > verify-alg "sha256";
> > > shared-secret "secret123";
> > > max-buffers 36864;
> > > rcvbuf-size 5242880;
> > > sndbuf-size 5242880;
> > > }
> > > }
> > > 
> > > Respectfully,
> > > Tyler
> > 
> > 
> > 
> > 
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