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What is the benefit of iSCSI?

Posted: Thu Sep 17, 2009 8:54 pm
by crushdepth
Can someone fill me in - what is the benefit of iSCSI? How is this different or better to a standard network share? What's the point of it all? Is it faster?

Re: What is the benefit of iSCSI?

Posted: Thu Sep 17, 2009 9:15 pm
by Q

it's a good solution when you have an application that has problems with network shares for some reason. when you connect an iscsi target it's for the OS like you would connect a local harddisk. with windows you can format it as ntfs (and for example use as storage extension for something like an exchange server or symantec backupexec). connected to a windows server, you can still configure all the detailed AD ACL rules which would be impossible otherwise. and under mac os x you can format it with hfs+. i also often read in the forum people use it together with a vmware server.

usually it should also be a bit faster compared with smb.

but you can/should only connect one initiator per target, so basically it's a dedicated storage over network, not a network share. anyway you can create up to 8 targets on the TS.

Re: What is the benefit of iSCSI?

Posted: Tue Sep 22, 2009 5:14 pm
by nolme

thanks for these informations.

I have some complementary questions.
You say that TS support only 8 iSCSI targets. Is this value the same for TS-809U-RP too ?

I've seen on a french tutorial that multiple access from different iniators is not recommanded. Is this only (for example) for 2 people accessing Excel file at the same time or is this a general feature to avoid multiple read/write access from differents sources ?

Can we use it safely trough WAN or must we use a VPN ?

If we have more than 10 remote NAs to backup on the 809U, is there a better way than iscsi ?



Re: What is the benefit of iSCSI?

Posted: Tue Sep 22, 2009 5:31 pm
by Q

yes currently it's 8 targets for all TS, maybe that will change in future.

you should not connect to the same target from different initiators, that's true. because it's like a local hdd, it most likely would corrupt data when 2 different users are accessing it. you should generally avoid it. it's just how iscsi is intended to work. because as said it's not a share, it's a dedicated storage via ethernet.

you can/should have only 1 initiator per target. that means the TS can be used for 8 initiators. only if you have something like a cluster - multiple servers with one central control/os - you could connect multiple initiators from that cluster to one target on the TS (because the cluster acts like 1 client).

if you want to share the same data for everbody, you should not use iscsi. only if you have a windows server and connect it to a TS iscsi target, you can of course create a share on the windows server which is on that target (so all access goes over the windows server).

afaik iscsi does not work reliable over internet, because it doesn't like packet loss and delays. although iscsi is an abbreviation of Internet Small Computer System Interface ;) but in fact that doesn't mean the internet, it just means IP-based storage in local lan... and IP (like in TCP/IP) is short for Internet Protocol. even i forget that sometimes ^^

i suggest you use the rsync protocol (qnap uses it for the remote replication feature) for backup over internet. it works great between qnap TS, copies just the differences and you can encrypt the transport (so a vpn isn't necessary). there is also a windows client/server named deltacopy in case you need it.