Hot answers tagged

23

There is no problem. Even if there is still available RAM, the Linux Kernel will move memory pages which are hardly ever used into swap space. It’s good to swap out memory pages that have been inactive for a while, keeping often-used data in cache; this is the desired situation of the Kernel. You can have more control on this by using vfs_cache_pressure (...


21

Because: Very, very bad things will happen if someone gains unauthorized access to your storage network Very, very bad things will happen if you have your iSCSI traffic not separated, and someone finds it a great idea to muck around with the STP topology at an edge switch, with the result of your entire network AND your storage subsystem going down at once ...


20

Short answer: This is the results of network latency and a serial workload (as you imposed by using direct=1, sync=1 and iodepth=1). Long answer: using direct=1, sync=1 and iodepth=1 you created a serial workload, as new writes can not be queued before the previous write was committed and confirmed. In other word, writes submission rate strictly depend on ...


17

To have multiple initiators share a single target, whether over ISCSI, Fibre Channel or other SAN solution, you need a cluster-aware filesystem. VMWare ESXi does this with VMFS. Veritas offers one in Veritas Cluster Suite. Sun offered one back in the day that would cause no end of troubles. Oracle did this with RAC, until they got wise and changed to ...


15

You need to have some sort of either a clustered file system or distributed lock manager to avoid metadata damage done to your file system with concurrent writes. There's a good summary of this issue on StarWind forum. https://forums.starwindsoftware.com/viewtopic.php?f=5&t=1392


13

Use LACP for NFS. Use MPIO for iSCSI. If your hypervisor hosts don't have storage interface redundancy, that's where you should focus your attention; no hacks, no bullshit. Add an additional NIC to your hosts and configure MPIO.


12

If each host only has one interface for iSCSI, then you won't be able to use MPIO with the setup you've described here. However, you should be able to configure the FreeNAS system to use Link Aggregation (LACP), so that you can service two hosts simultaneously each at 1Gb (for a total of 2Gb from the FreeNAS). Instead of MPIO, look into LACP (or, get a ...


11

To squeeze maximum performance out of iSCSI connected storage you should use Jumbo Frames and MPIO (not LACP). RDMA/iSER is recommended if you can do that. AOE (ATA over Ethernet) is old and is shit. We’ve got rid of Coraid years ago, already. We are using StarWind https://www.starwindsoftware.com/ as iSCSI target quite a while already and StarWind asked ...


8

The rationale behind this in RFC 3720 is that above all, IQNs should be unique. The date prepended is a reasonable guarantee that the entity that controlled the domain name represented (in the naming auth field) at that time a "naming authority" who could ensure uniqueness - domain names change hands all the time and since the only other unique stuff going ...


8

Any online writable disk can be corrupted by a malicious software or user. Underestimating them by assuming they cannot find a file share is a mistake. Last line of defense for important data is always tested, cold offline backups. And in this case, the important data may include backups themselves! Think about the possible ways to make backup archives ...


7

If you do have just one Synology box shared between your Hyper-V machines, it can still be considered as a SPoF. It dies, you lose all the LUNs sitting there. For true HA you would need a second NAS box and some replication mechanism. Well, one thing that comes to mind is HA cluster with two Synology NAS devices. But AFAIK it doesnt rate well in the world of ...


7

I see similar issue posted on technet. Is there any chance to see what does Event Log show? For the case, from my experience, Microsoft iSCSI target is too slow. Currently, I use StarWind Virtual SAN Free that delivers really fast iSCSI server with the additional functionality of cache and log-structured file system (snapshots, dedupe, etc.). I suggest you ...


7

Using one drive for multiple connections without clustered file system is a suicide. Data corruption is the first that you will see after a few data iterations. You must run clustered file system to avoid such issues. There are a lot of topics answering such scenario, but this one is my favorite. https://forums.starwindsoftware.com/viewtopic.php?f=5&t=...


7

First off, get rid of NIC teams for your storage and synchronization networks. ISCSI networks leverage MPIO, there is no need for trunking, teaming, bonding, etc. Also, don't forget to enable MPIO in Add Roles and Features wizard. Assuming you want to use the 10.0.0.x networks for iSCSI traffic, your ISCSI Initiator configuration should look like this: ...


7

This appears to happen when the system page file is located on the iSCSI device. While locating the page file on iSCSI worked fine under Windows 7, it appears to be broken in Windows 10. Unfortunately, Windows defaults to setting up a page file on the primary disk, so when the primary disk is iSCSI, it is broken out-of-the-box. (Note that the stop code ...


7

Good question. I think your sparse zvol block size should be 128k. Your ZIO scheduler settings should all be higher, like minimum 10 and max 64. zfs_txg_timeout should be much longer. I do 15 or 30s on my systems. I think the multiple RAIDZ3's (or was that a typo) are overkill and play a big part in the performance. Can you benchmark with RAIDZ2? Edit: ...


7

iSCSI as a protocol is not limiting performance or latency on spindle (HDD) drives. It may limit on SSD and will limit on NVMe. The performance in this case depends on: 1) Physical storage. You can increase amount of disk in RAID and use RAID10 for the best one. Video streaming uses large blocks, so properly aligned stripe size may also help. 2) Network ...


7

That is normal behavior for a non-clustered file system. To use iSCSI SAN with Ubuntu compute servers, a clustered file system should be used. You should probably learn more about GPFS, GFS2, Lustre, GlusterFS, and OCFS2 and use one of them on top of iSCSI SAN. Edit: Good description of what’s going on can be found here: https://forums.starwindsoftware.com/...


7

Leaving the question of iSCSI vulnerability when using it without a clustered file system but with multiple initiators aside, I can hardly find any clear reason why file sharing protocol would be more secure in terms of ransomware comparing to iSCSI. You get CHAP to strengthen authentication and IPSec to secure data transfer over the network. Here is a good ...


6

Nothing REQUIRES VLAN separation. Switches don't automatically do anything except SWITCH traffic. That being said, your design looks perfectly OK. You're segregating your public and private traffic and you're isolating your iSCSI traffic. You could put all of the internal traffic (including the iSCSI traffic) on a single VLAN but that's not recommended ...


6

Get a NAS instead of a SAN and export the file system via NFS. As you've discovered SANs share block storage via networking protocols like iSCSI, ATAoE, or FibreChannel. NAS devices share file systems over protocols such as NFS, CIFS/SMB, WebDAV, and possibly others. See also: What is the difference between SAN, NAS and DAS?


6

From http://technet.microsoft.com/en-us/library/ee619752(v=WS.10).aspx Configure the MPIO Failback policy setting If you use the Failover Only load-balancing policy setting, MPIO failback allows the configuration of a preferred I/O path to the storage, and allows automatic failback to be the preferred path if desired. Consider the following scenario: • ...


6

No there wont be any down time, this really is a standard thing to do now in enterprise, where always up availability is key. LVM does this expansion in the background and it is pretty much instant, it wont have any effect on services, I do this once or twice a week on my estate and haven't had a problem yet


6

Because not doing so allows regular traffic to impact on storage traffic, which is a bad idea as it means that say a user's download could delay an important read or write.


6

I am presented with SMB, NFS and iSCSI options to connect to the server. Meaning, I have the option of either setting up a share via NFS or SMB or creating a virtual iSCSI drive in which I can connect to. For direct connection to a server—for true server related storage—iSCSI is the way to go. And you would then manage the user access—via SMB/CIFS or ...


6

Network filesystems and databases can be a problematic combo, and at least InnoDB does not like NFS. From the MySQL documentation If reliability is a consideration for your data, do not configure InnoDB to use data files or log files on NFS volumes. Potential problems vary according to OS and version of NFS, and include such issues as lack of ...


6

iSCSI will be fine here, especially since you already have so much of the infrastructure for it. While fiber would be less susceptible to interference, a 2Gb/s difference is enough to make up for that in typical situations. iSCSI is capable of being routed (since it uses IP), if that interests you at all. Also, the fiber HBAs and cable are consistently more ...


6

Your expectation on how Ethernet link aggregation works are incorrect. All aggregation methods other than balance-rr (ie: all methods whose mode > 0) do not give you a greater single-connection throughput; rather, they increase total available bandwidth when multiple connections are established from/to the affected hosts. In other words, LAG/LACP will not ...


6

To get disk image do P2V and/or V2V: attach iSCSI to Windows by ISCSI initialtor. create VHDX using Disk2vhd (https://technet.microsoft.com/en-us/sysinternals/ee656415.aspx) convert VHDX to QCOW using StarWind V2V then use disk image for (https://www.starwindsoftware.com/converter) To move image to physical host do P2P and/or V2P with help of clonezilla ...


6

The fileio backing store driver is the way you would accomplish this. Consistency is only a concern if you choose to enable writeback caching (or as targetcli refers to it, "buffered mode") on the fileio backstores. Unbuffered mode is the default for just about every targetcli implementation on any distro, as suggested by Datera itself. This shouldn't be a ...


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