Just wondering if anyone has had any experience with this.
I''m thinking about setting up a 2-drive RAID1 set using Linux software
RAID. The question is, as far as performance is concerned, which is
better:
* Let dom0 handle the RAID and pass the volume to domU or
* Pass both drives to domU and let it handle the RAID.
thanks in advance,
-m
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Petersson, Mats
2007-Feb-01 15:38 UTC
RE: [Xen-users] Linux software RAID1 (Dom0 or domU)?
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marduk > Sent: 01 February 2007 15:29 > To: xen-users@lists.xensource.com > Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > Just wondering if anyone has had any experience with this. > > I''m thinking about setting up a 2-drive RAID1 set using Linux software > RAID. The question is, as far as performance is concerned, which is > better: > > * Let dom0 handle the RAID and pass the volume to domU or > * Pass both drives to domU and let it handle the RAID.I would have thought that the performance penalty for software raid would be about equal - however, there is a difference between loading Dom0 and DomU if you have more than one guest-domain - Dom0 will be used by all domains, so any extra load on Dom0 will affect all domains, whilst extra load in DomU only affects that DomU. Particulary, latency for each domain will be higher if Dom0 is handling the raid. That''s my thoughts on the subject, and be aware that I''ve never run software raid on any system ever! -- Mats> > thanks in advance, > -m > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mats, The problem when you use guest domain to create MD-RAID array is that the array will only be visible to that guest domain. If we create array in domain0, we can make it visible to all guest domains. I think this is also the benefit to use domain0 to manage MD-RAID array. Regards, Liang ----- Original Message ----- From: "Petersson, Mats" <Mats.Petersson@amd.com> To: "Marduk" <xen@marduk.letterboxes.org>; <xen-users@lists.xensource.com> Sent: Thursday, February 01, 2007 8:38 AM Subject: RE: [Xen-users] Linux software RAID1 (Dom0 or domU)?> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marduk > Sent: 01 February 2007 15:29 > To: xen-users@lists.xensource.com > Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > Just wondering if anyone has had any experience with this. > > I''m thinking about setting up a 2-drive RAID1 set using Linux software > RAID. The question is, as far as performance is concerned, which is > better: > > * Let dom0 handle the RAID and pass the volume to domU or > * Pass both drives to domU and let it handle the RAID.I would have thought that the performance penalty for software raid would be about equal - however, there is a difference between loading Dom0 and DomU if you have more than one guest-domain - Dom0 will be used by all domains, so any extra load on Dom0 will affect all domains, whilst extra load in DomU only affects that DomU. Particulary, latency for each domain will be higher if Dom0 is handling the raid. That''s my thoughts on the subject, and be aware that I''ve never run software raid on any system ever! -- Mats> > thanks in advance, > -m > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, 2007-02-01 at 09:37 -0700, Liang Yang wrote:> Mats, > > The problem when you use guest domain to create MD-RAID array is that the > array will only be visible to that guest domain. If we create array in > domain0, we can make it visible to all guest domains. > > I think this is also the benefit to use domain0 to manage MD-RAID array. >For my purposes the array will dedicated to a single domU. I am mainly concerned with performance. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Mats, > > The problem when you use guest domain to create MD-RAID array is that the > array will only be visible to that guest domain. If we create array in > domain0, we can make it visible to all guest domains. > > I think this is also the benefit to use domain0 to manage MD-RAID array. > > Regards, > > Liang > > ----- Original Message ----- > From: "Petersson, Mats" <Mats.Petersson@amd.com> > To: "Marduk" <xen@marduk.letterboxes.org>; <xen-users@lists.xensource.com> > Sent: Thursday, February 01, 2007 8:38 AM > Subject: RE: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > > > >> -----Original Message----- >> From: xen-users-bounces@lists.xensource.com >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marduk >> Sent: 01 February 2007 15:29 >> To: xen-users@lists.xensource.com >> Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)? >> >> Just wondering if anyone has had any experience with this. >> >> I''m thinking about setting up a 2-drive RAID1 set using Linux software >> RAID. The question is, as far as performance is concerned, which is >> better: >> >> * Let dom0 handle the RAID and pass the volume to domU or >> * Pass both drives to domU and let it handle the RAID. > > I would have thought that the performance penalty for software raid > would be about equal - however, there is a difference between loading > Dom0 and DomU if you have more than one guest-domain - Dom0 will be used > by all domains, so any extra load on Dom0 will affect all domains, > whilst extra load in DomU only affects that DomU. Particulary, latency > for each domain will be higher if Dom0 is handling the raid. > > That''s my thoughts on the subject, and be aware that I''ve never run > software raid on any system ever! > > -- > Mats >> >> thanks in advance, >> -m >> >> >> _______________________________________________ >> Xen-users mailing list >> Xen-users@lists.xensource.com >> http://lists.xensource.com/xen-users >> >> >> > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >Wouldn''t there be a performance impact if the RAID was in a DomU? Every I/O request would have to go through a hypercall to the Dom0 to perform the I/O task and then send the data back. And since this is software RAID it isn''t a single I/O request, it is *potentially* (depending on the RAID level) an I/O request per drive in the RAID. While the Dom0 is not running the actual RAID algorithms (mdadm stuff, or raidtools for the older crowd) it is still handling alot of I/O and the associated overhead for the hypercalls for each request. I understand what Mats is saying about putting it in a DomU will not starve ALL the other DomU''s as if it is in Dom0, but it really isn''t saving the Dom0 much work. Since Xen is currently prone to I/O wait issues with alot of DomU''s I would strongly suggest getting a hardware RAID card unless the server has alot of processing power and not alot of I/O intesive DomU''s on it. Just my thoughts. Ryan _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Petersson, Mats
2007-Feb-01 16:56 UTC
RE: [Xen-users] Linux software RAID1 (Dom0 or domU)?
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Ryan Burke > Sent: 01 February 2007 16:47 > To: Liang Yang > Cc: Marduk; Petersson, Mats; xen-users@lists.xensource.com > Subject: Re: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > > Mats, > > > > The problem when you use guest domain to create MD-RAID > array is that the > > array will only be visible to that guest domain. If we > create array in > > domain0, we can make it visible to all guest domains. > > > > I think this is also the benefit to use domain0 to manage > MD-RAID array. > > > > Regards, > > > > Liang > > > > ----- Original Message ----- > > From: "Petersson, Mats" <Mats.Petersson@amd.com> > > To: "Marduk" <xen@marduk.letterboxes.org>; > <xen-users@lists.xensource.com> > > Sent: Thursday, February 01, 2007 8:38 AM > > Subject: RE: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > > > > > > > > >> -----Original Message----- > >> From: xen-users-bounces@lists.xensource.com > >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marduk > >> Sent: 01 February 2007 15:29 > >> To: xen-users@lists.xensource.com > >> Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)? > >> > >> Just wondering if anyone has had any experience with this. > >> > >> I''m thinking about setting up a 2-drive RAID1 set using > Linux software > >> RAID. The question is, as far as performance is > concerned, which is > >> better: > >> > >> * Let dom0 handle the RAID and pass the volume to domU or > >> * Pass both drives to domU and let it handle the RAID. > > > > I would have thought that the performance penalty for software raid > > would be about equal - however, there is a difference > between loading > > Dom0 and DomU if you have more than one guest-domain - Dom0 > will be used > > by all domains, so any extra load on Dom0 will affect all domains, > > whilst extra load in DomU only affects that DomU. > Particulary, latency > > for each domain will be higher if Dom0 is handling the raid. > > > > That''s my thoughts on the subject, and be aware that I''ve never run > > software raid on any system ever! > > > > -- > > Mats > >> > >> thanks in advance, > >> -m > >>[snip list gunk]> > Wouldn''t there be a performance impact if the RAID was in a > DomU? Every > I/O request would have to go through a hypercall to the Dom0 > to perform > the I/O task and then send the data back. And since this is > software RAID > it isn''t a single I/O request, it is *potentially* (depending > on the RAID > level) an I/O request per drive in the RAID. While the Dom0 > is not running > the actual RAID algorithms (mdadm stuff, or raidtools for the > older crowd) > it is still handling alot of I/O and the associated overhead for the > hypercalls for each request. I understand what Mats is saying about > putting it in a DomU will not starve ALL the other DomU''s as > if it is in > Dom0, but it really isn''t saving the Dom0 much work. > > Since Xen is currently prone to I/O wait issues with alot of DomU''s I > would strongly suggest getting a hardware RAID card unless > the server has > alot of processing power and not alot of I/O intesive DomU''s on it. > > Just my thoughts.Very good points (I did say that I had never run software raid!) The increase in I/O requests from DomU to Dom0 will be adding to the Dom0 load if DomU is doing the software raid, that is correct. Of course, that''s less load in Dom0 than also doing the software raid functionality itself, but it even further increases the IO latency, compared to doing two requests within Dom0. I agree that hardware raid is the leanest option (cpu-wise, maybe not for the bank). -- Mats> > Ryan > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thursday 01 February 2007, Petersson, Mats wrote:> I agree that hardware raid is the leanest option (cpu-wise, maybe not > for the bank).most ''hardware raid'' cards are far worse, both in performance and cpu-usage, than the linux md module. also, in RAID 1 all writes are done twice, so it has to go twice through dom0. i guess it''s a far worse thing than doing it all in dom0. the md module is _very_ lean and optimised. for RAID 5 it might be even worse to do in domU, because to get good performance it''s very important to get whole stripes in cache. to do in dom0 you''d need more RAM there than the minimum, but in several domU you''d have to get the same ''extra'' several times. and, of course, if you do in Dom0, you can split it with LVM, and all domU''s benefit. -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Feb-01 18:02 UTC
Re: [Xen-users] Linux software RAID1 (Dom0 or domU)?
I think I''d do RAID in dom0... It makes configuration changes easy to do without fiddling with the guest and will free up some space in the block ring (although I''m not convinced that''ll make much difference to performance). Moreover, this is future-proofed: if you wanted to upgrade to hardware RAID at some point (or change the RAID level used) you can do it without fiddling inside one or more guests. Hardware RAID or hardware-assisted RAID (I understand some SATA controllers can now submit a write simultaneously to multiple drives to accelerate software RAID1, although I''m not sure Linux supports this yet) would also require that dom0 was doing the RAID. HTH, Cheers, Mark On Thursday 01 February 2007 16:56, Petersson, Mats wrote:> > -----Original Message----- > > From: xen-users-bounces@lists.xensource.com > > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Ryan Burke > > Sent: 01 February 2007 16:47 > > To: Liang Yang > > Cc: Marduk; Petersson, Mats; xen-users@lists.xensource.com > > Subject: Re: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > > > > Mats, > > > > > > The problem when you use guest domain to create MD-RAID > > > > array is that the > > > > > array will only be visible to that guest domain. If we > > > > create array in > > > > > domain0, we can make it visible to all guest domains. > > > > > > I think this is also the benefit to use domain0 to manage > > > > MD-RAID array. > > > > > Regards, > > > > > > Liang > > > > > > ----- Original Message ----- > > > From: "Petersson, Mats" <Mats.Petersson@amd.com> > > > To: "Marduk" <xen@marduk.letterboxes.org>; > > > > <xen-users@lists.xensource.com> > > > > > Sent: Thursday, February 01, 2007 8:38 AM > > > Subject: RE: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > > > > >> -----Original Message----- > > >> From: xen-users-bounces@lists.xensource.com > > >> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marduk > > >> Sent: 01 February 2007 15:29 > > >> To: xen-users@lists.xensource.com > > >> Subject: [Xen-users] Linux software RAID1 (Dom0 or domU)? > > >> > > >> Just wondering if anyone has had any experience with this. > > >> > > >> I''m thinking about setting up a 2-drive RAID1 set using > > > > Linux software > > > > >> RAID. The question is, as far as performance is > > > > concerned, which is > > > > >> better: > > >> > > >> * Let dom0 handle the RAID and pass the volume to domU or > > >> * Pass both drives to domU and let it handle the RAID. > > > > > > I would have thought that the performance penalty for software raid > > > would be about equal - however, there is a difference > > > > between loading > > > > > Dom0 and DomU if you have more than one guest-domain - Dom0 > > > > will be used > > > > > by all domains, so any extra load on Dom0 will affect all domains, > > > whilst extra load in DomU only affects that DomU. > > > > Particulary, latency > > > > > for each domain will be higher if Dom0 is handling the raid. > > > > > > That''s my thoughts on the subject, and be aware that I''ve never run > > > software raid on any system ever! > > > > > > -- > > > Mats > > > > > >> thanks in advance, > > >> -m > > [snip list gunk] > > > Wouldn''t there be a performance impact if the RAID was in a > > DomU? Every > > I/O request would have to go through a hypercall to the Dom0 > > to perform > > the I/O task and then send the data back. And since this is > > software RAID > > it isn''t a single I/O request, it is *potentially* (depending > > on the RAID > > level) an I/O request per drive in the RAID. While the Dom0 > > is not running > > the actual RAID algorithms (mdadm stuff, or raidtools for the > > older crowd) > > it is still handling alot of I/O and the associated overhead for the > > hypercalls for each request. I understand what Mats is saying about > > putting it in a DomU will not starve ALL the other DomU''s as > > if it is in > > Dom0, but it really isn''t saving the Dom0 much work. > > > > Since Xen is currently prone to I/O wait issues with alot of DomU''s I > > would strongly suggest getting a hardware RAID card unless > > the server has > > alot of processing power and not alot of I/O intesive DomU''s on it. > > > > Just my thoughts. > > Very good points (I did say that I had never run software raid!) > > The increase in I/O requests from DomU to Dom0 will be adding to the > Dom0 load if DomU is doing the software raid, that is correct. Of > course, that''s less load in Dom0 than also doing the software raid > functionality itself, but it even further increases the IO latency, > compared to doing two requests within Dom0. > > I agree that hardware raid is the leanest option (cpu-wise, maybe not > for the bank). > > -- > Mats > > > Ryan > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users-- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Luke S. Crawford
2007-Feb-01 19:17 UTC
Re: [Xen-users] Linux software RAID1 (Dom0 or domU)?
On Thu, 1 Feb 2007, Mark Williamson wrote:> I think I''d do RAID in dom0... It makes configuration changes easy to do > without fiddling with the guest and will free up some space in the block ring > (although I''m not convinced that''ll make much difference to performance).Hm. I''m interested in this discussion because I have a fibre-channel setup with lots of disks, but no raid head. Right now, we are running md software raids in Dom0 as you suggest; the primary problem with this is that hot-migration won''t work; all my Dom0s can see all the disks, (well, depending on how I setup zoning) but the MD devices only exist on the server that created them, so I believe hot-migration or even having half of one md on one server and half of the same md on another server just won''t work. One way to solve this is to make clvm support mirroring; but I''m too dumb to write that code myself. the other solution would be to make every physical disk a clvm VolumeGroup; then make sure that every DomU have 2 equaly-sized partitions from different volume groups. The DomU can then mirror or stripe the disks as required. (this has actually been a pretty hot internal prgmr.com debate; the best solution, we all agree, is to get a hardware-raid device, but we haven''t done so yet, mostly because I''m cheap. disks and fibre switches are commodity, raid-heads are decidedly not.) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Jensen Nathan A Capt USAFA/DFCS
2007-Feb-01 23:04 UTC
RE: [Xen-users] Linux software RAID1 (Dom0 or domU)?
Great conversation! This dovetails nicely into some of the design considerations that I am now considering. I have the opportunity to design a new datacenter from the ground up, and Xen virtualization sounds like an awesome way to go. However, I would like to try and make things as reliable (while not necessarily complicated) as possible, since the control center is NOT co-located with the datacenter. Money is also somewhat tight. My initial thoughts go something like this: 1. Build several robust servers with large RAID storage space 2. The only purpose for these machines is to serve storage 3. Use LVM to create partitions on the raid servers as needed 4. Buy commodity servers to serve as Dom0''s 5. Dom0''s can see block devices on large RAID using AoE 6. DomU''s can be created on commodity servers using RAID as storage 7. Use an NFS share to maintain all of the xen config files What this buys me: 1. If commodity server dies, just point a different commodity server at the right partition and restore 2. All commodity servers can see RAID LVM partitions -- I can now do hot-swapping of domU instances -- I don''t think I''ll need a CFS like GFS 3. Data storage should be fairly reliable using the RAID servers 4. I can recover from any failure, (except extreme hardware failure on a RAID server), without leaving the remote control center My fear is: 1. I am totally hosed if my RAID server tanks What is your take on this configuration? Does anyone have recommendations for quickly recovering from a RAID server crash in this scenario? What about AoE? Would I be better served to pay the money and go fibre-channel? Thanks for the discussion, Nate -----Original Message----- From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Luke S. Crawford Sent: Thursday, February 01, 2007 12:17 PM To: Mark Williamson Cc: xen-users@lists.xensource.com Subject: Re: [Xen-users] Linux software RAID1 (Dom0 or domU)? On Thu, 1 Feb 2007, Mark Williamson wrote:> I think I''d do RAID in dom0... It makes configuration changes easy todo> without fiddling with the guest and will free up some space in theblock ring> (although I''m not convinced that''ll make much difference toperformance). Hm. I''m interested in this discussion because I have a fibre-channel setup with lots of disks, but no raid head. Right now, we are running md software raids in Dom0 as you suggest; the primary problem with this is that hot-migration won''t work; all my Dom0s can see all the disks, (well, depending on how I setup zoning) but the MD devices only exist on the server that created them, so I believe hot-migration or even having half of one md on one server and half of the same md on another server just won''t work. One way to solve this is to make clvm support mirroring; but I''m too dumb to write that code myself. the other solution would be to make every physical disk a clvm VolumeGroup; then make sure that every DomU have 2 equaly-sized partitions from different volume groups. The DomU can then mirror or stripe the disks as required. (this has actually been a pretty hot internal prgmr.com debate; the best solution, we all agree, is to get a hardware-raid device, but we haven''t done so yet, mostly because I''m cheap. disks and fibre switches are commodity, raid-heads are decidedly not.) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thursday 01 February 2007, Jensen Nathan A Capt USAFA/DFCS wrote:> My fear is: > > 1. I am totally hosed if my RAID server tanksthe ''standard'' answer would be: "do a mirror (RAID 1) of your RAID boxes"; but i think this could be interpreted at least two ways: A) - set your RAID servers in pairs - use md to do RAID1 of each pair - each RAID1 (of two RAID servers) is one PV in your big VG .... but it''s not clear ''who'' does that RAID1 B) - each RAID server is one PV in your big VG - create two LVs for each volume you want, make sure they''re on different PVs - do a RAID1 of those two LVs - feed that RAID1 device to Xen since each volume is used only by one DomU at a time, it''s clear that each RAID1 is responsibility of only one Dom0 .... but i don''t think md can take a pair of LVs to create a RAID1 so i wonder, can EVMS do it? i guess it can do something like (B), but don''t know it by heart -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 1 Feb 2007 at 9:29, Marduk wrote:> Just wondering if anyone has had any experience with this. > > I''m thinking about setting up a 2-drive RAID1 set using Linux software > RAID. The question is, as far as performance is concerned, which is > better: > > * Let dom0 handle the RAID and pass the volume to domU or > * Pass both drives to domU and let it handle the RAID.Hi! If you think about the reasons of having a RAID1, which domains would be affected by a hardware failure, and what would you have to do then? If you think about it, everything seems logical. To avoid needless work and overly complex configurations, I''d mirror in Dom0 and export mirrored devices to DomU. Regards, Ulrich _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Friday 02 February 2007 00:48, Javier Guerra wrote:> On Thursday 01 February 2007, Jensen Nathan A Capt USAFA/DFCS wrote: > > My fear is: > > > > 1. I am totally hosed if my RAID server tanks > > the ''standard'' answer would be: "do a mirror (RAID 1) of your RAID boxes"; > but i think this could be interpreted at least two ways: > > A) > - set your RAID servers in pairs > - use md to do RAID1 of each pair > - each RAID1 (of two RAID servers) is one PV in your big VG > > .... but it''s not clear ''who'' does that RAID1 > > B) > - each RAID server is one PV in your big VG > - create two LVs for each volume you want, make sure they''re on different > PVs - do a RAID1 of those two LVs > - feed that RAID1 device to Xen > > since each volume is used only by one DomU at a time, it''s clear that each > RAID1 is responsibility of only one Dom0 > > .... but i don''t think md can take a pair of LVs to create a RAID1 > > so i wonder, can EVMS do it? i guess it can do something like (B), but > don''t know it by heartor C) - build pairs of RAID servers - replicate storage with drbd - create LVs on the storage and - export to dom0''s using iSCSI or AoE... This gives you redundancy of storage, though you''ll still need some form of backup to deal with any potential filesystem corruption, as drbd replicates everything. Live migration works well as all the xen servers connect to the iSCSI/AoE devices permanently and you''ve got a consistent device naming scheme for the vdb''s in the vm configs. Our setup is two 16-disk RAID storage boxes running drbd and iscsitarget and multiple xen boxes running open-iscsi in dom0. Eventually, the storage boxes will end up in different buildings to allow for low level power outages and problems with the laboratory infrastructure. The Xen boxes could be anywhere on site. Matthew -- Matthew Wild Tel.: +44 (0)1235 445173 M.Wild@rl.ac.uk URL http://www.ukssdc.ac.uk/ UK Solar System Data Centre and World Data Centre - Solar-Terrestrial Physics, Chilton Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users