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

[Tyler Phillippe]

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

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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